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Unformatted text preview: Journal of Economic Literature 2010, 48:1, 3–57
http:www.aeaweb.org/articles.php?doi=10.1257/jel.48.1.3 Civil War
Christopher Blattman and Edward Miguel*
Most nations have experienced an internal armed conflict since 1960. Yet while
civil war is central to many nations’ development, it has stood at the periphery of
economics research and teaching. The past decade has witnessed a long overdue
explosion of research into war’s causes and consequences. We summarize progress,
identify weaknesses, and chart a path forward. Why war? Existing theory is provocative but incomplete, omitting advances in behavioral economics and making
little progress in key areas, like why armed groups form and cohere, or how more
than two armed sides compete. Empirical work finds that low per capita incomes
and slow economic growth are both robustly linked to civil war. Yet there is little consensus on the most effective policies to avert conflicts or promote postwar
recovery. Cross-country analysis of war will benefit from more attention to causal
identification and stronger links to theory. We argue that micro-level analysis and
case studies are also crucial to decipher war’s causes, conduct, and consequences.
We bring a growth theoretic approach to the study of conflict consequences to highlight areas for research, most of all the study of war’s impact on institutions. We
conclude with a plea for new and better data. ( JEL D72, D74, O17) 1. Civil War and the Study of Economics I nternal civil conflict has been commonplace during the past half-century, a
fact that, until recently, escaped the notice
of most economists. Civil wars, or those i
nternal conflicts that count more than
1,000 battle deaths in a single year, have
afflicted a third of all nations. Counting
civil conflicts, or those that count at least
wenty-five battle deaths per annum,
increases the incidence to more than * Blattman: Yale University. Miguel: University of
California, Berkeley and NBER. We thank Ana Arjona,
Karen Ballentine, Bob Bates, Tim Besley, David Card,
Ernesto Dal Bó, Jesse Driscoll, Bill Easterly, Jim Fearon,
Karen Ferree, Mary Kay Gugerty, Anke Hoeffler, Patricia Justino, Stathis Kalyvas, David Leonard, Jason Lyall,
Andrew Mack, Daniel Maliniak, Gerard Padro-i-Miquel,
Torsten Persson, Dan Posner, Robert Powell, Vijaya Ramachandran, Debraj Ray, Marta Reynal-Querol, Gérard
Roland, Shanker Satyanath, Jacob Shapiro, Ryan Sheely, Stergios Skaperdas, Abbey Steele, Julia Strauss, Dennis de
Tray, Philip Verwimp, Barbara Walter, Jeremy Weinstein,
our anonymous referees and the editor, Roger Gordon, for
comments and discussion. We are deeply grateful to our
coauthors on related research: Jeannie Annan, Samuel
Bazzi, Bernd Beber, John Bellows, Khristopher Carlson,
John Dykema, Rachel Glennerster, Dyan Mazurana,
Gerard Roland, Sebastian Saiegh, Shanker Satyanath, and
Ernest Sergenti. Camille Pannu, Abbey Steele, and Melanie Wasserman provided superb research assistance. 3 4 Journal of Economic Literature, Vol. XLVIII (March 2010) half.1 This internal warfare is not just extremely
common, it is also persistent. Figure 1 displays
the cumulative proportion of all nations experiencing wars and conflicts since 1960. Twenty
percent of nations have experienced at least
ten years of civil war during the period.
The proportion of countries embroiled
in civil conflict at a single point in time
increased steadily through the last half of the
twentieth century, peaking in the 1990s at
over 20 percent (see figure 2). In sub-Saharan Africa, the world’s poorest region, nearly
a third of countries had active civil wars or
conflicts during the mid-1990s.2 The prevalence of war prompted scholars to ask a simple question: why there is so much civil war
in the world? A decade later, observers began
to ask where some of the civil wars had gone;
there were “just” thirty-two active conflicts
in 2006, the result of a steady decline in conflict from a peak of fifty-one in 1992.
The outbreak of internal wars is commonly
attributed to poverty. Indeed, the correlation
between low per capita incomes and higher
propensities for internal war is one of the
most robust empirical relationships in the literature. Figure 3 illustrates the relationship
between per capita income (percentiles) and
civil war using a nonparametric Fan regression; countries towards the bottom of the
world income distribution—many in Africa—
have several times more wars than those in
1 These definitions come from the well-known UCDP/
PRIO dataset developed by Nils Petter Gleditsch et
al. (2002) and extended in Lotta Harbom and Peter
Wallensteen (2007). UCDP/PRIO defines conflict as “a
contested incompatibility that concerns government and/
or territory where the use of armed force between two
parties, of which at least one is the government of a state,
results in at least 25 battle-related deaths.” As noted
below, the definition and coding of civil war is contested,
but our main points are robust to alternative approaches.
2 The proportion of individuals directly affected by
war violence is lower than suggested by this figure, as
many armed conflicts are confined to subregions. Yet
even individuals living in largely peaceful regions can be
adversely affected by insecurity, the public policy changes,
and economic consequences of a civil war. the top quartile, while middle income countries still face considerable conflict risk.
Yet claims of a direct causal line from poverty to conflict should be greeted with caution.
One reason is that this line can be drawn in
reverse. Conflicts devastate life, health, and
living standards. A chilling example is the
Democratic Republic of Congo, where surveys
suggest millions may have died as a result of
the recent civil war, primarily due to hunger
and disease (Benjamin Coghlan et al. 2007).
Although the accuracy of mortality figures in
such war zones is open to question, estimated
mortality figures for Rwanda, Angola, and
Sudan are likewise shocking. Massive loss of life
inevitably affects the economy. Warfare also
destroys physical infrastructure and human
capital, as well as possibly altering some social
and political institutions. Moreover, internal
wars are contagious; refugee flows, disease,
lawlessness, and the illicit trades in drugs,
arms, and minerals have generated “spillover”
effects into the countries neighboring conflict
zones. Some have argued that the destructive
consequences of internal warfare may be so
great as to be a factor in the growing income
gap between the world’s richest and poorest
nations (Paul Collier et al. 2003).
A seeming paradox, however, is that
warfare is also sometimes credited for the
echnological and institutional evelopment
that underpins Western economic rosperity.
Both internal and external wars are commonplace in European istory. Several
scholars have claimed that inter-state wars
and wars of territorial conquest served a
critical role in enabling the development of
strong and capable government institutions
in Europe (e.g., Daron Acemoglu and James
A. Robinson 2006; Niall Ferguson 2002;
Charles Tilly 1975; Tilly 1992). The evidence
on institution-building and internal warfare
is limited, but cases of stronger states emerging out of contemporary civil wars also exist
in East Africa and Southeast Asia (Dan Slater
2005; Jeremy M. Weinstein 2005a). Blattman and Miguel: Civil War 5 0.6 – Proportion of countries Proportion of countries with civil war
Proportion of countries with civil war or con ict 0.4 – 0.2 – – – – – – 0–
0 10 20 30 40 Number of years war and war or con ict
Figure 1: The Distribution of Civil War or Conflict Years across Countries, 1960–2006
Sources: Data based on UCDP/PRIO armed conflict database. Civil wars are those internal conflicts that count
more than 1,000 battle deaths in a single year. Civil war or conflict includes cases with at least twenty-five battle
deaths in a single year. It seems clear to us that civil war ought to be
central in the study of international conomic
development. Yet leading evelopment econod
mists have too often overlooked it; for instance,
two respected and widely taught undergraduate evelopment economics extbooks (Debraj
Ray 1998; Michael Todaro 1999) do not contain the words “war,” “conflict,” or “violence”
in their subject index. Moreover, a 2007
survey (by the authors) of sixty-three development economics course syllabi in leading
U.S. universities reveals that only 13 percent
of undergraduate courses and 24 percent of graduate courses mention any of these topics
at all.3 Over the past decade, however, many
economists and other social scientists have
worked to better understand the causes and
the economic legacies of internal warfare,
often in collaboration with political cientists
and other scholars. This article’s main goal is to
summarize this progress and help chart a productive path forward. As befits an merging
field, this article focuses as much on what we
cannot say today as what we know.
Unfortunately, our survey deals too briefly
with important topics such as civil war endings
3 The survey included thirty-eight undergraduate and
twenty-five graduate syllabi. We searched for online syllabi
for undergraduate institutions ranked in the top fifty of the
U.S. News and World Report college rankings (2007a), and for Ph.D. economics programs ranked in the top twentyfive of either the National Research Council (1995), Piper
Fogg (2007), or U.S. News and World Report economics
PhD (2007b) ranking. Details are available upon request. Journal of Economic Literature, Vol. XLVIII (March 2010) 6
0.25 – Proportion of countries 0.2 – 0.15 – 0.1 –
Proportion of countries with civil war
Proportion of countries with civil war or con ict – – – – – 0.05 –
1960 1970 1980 1990 2000 Year
Figure 2: Proportion of Countries with an Active Civil War or Civil Conflict, 1960–2006
Sources: Data based on UCDP/PRIO armed conflict database (Gleditsch et al. 2002). Civil wars are those
internal conflicts that count more than 1,000 battle deaths in a single year. Civil war or conflict includes cases
with at least twenty-five battle deaths in a single year. and duration, postwar reconstruction, and
the emergence of peaceable institutions, in
part because these subliteratures are still
largely in flux. We must also neglect related
forms of violence—interstate war, terrorism, coups, communal violence, political
repression, and crime—to keep this article
a reasonable length. This is a pity because the distinction between civil wars and other
forms of political instability has largely
been assumed rather than demonstrated.4
Our principal conclusions challenge
researchers to focus on new questions,
econometric methods, and data. First,
beginning with the origins of conflict, we
argue that existing theory is incomplete. 4 Related literatures investigate the logic and
organization of terrorism, including: self-selection
and screening of terrorist recruits (Ethan Bueno de
Mesquita 2005); why radical religious clubs specialize in suicide attacks (Eli Berman and David D. Laitin
2008); how terrorist organizations use bureaucracy to
align the asymmetric preferences for violence among
leaders and operatives (Jacob N. Shapiro 2008); the
economic logic of ostage-taking and government
response (Todd Sandler and Walter Enders 2004); the
splintering and ideology of terrorist groups (Bueno de Mesquita 2008); the logic of suicide missions (Diego
Gambetta 2005); and why terrorists employ roadside
bombs (Matthew A. Hanson 2007). The line between
rebel and terrorist groups is blurry, and many of the
lessons we draw may apply to terrorism. Further theoretical work laying out the analytical distinctiveness of
civil wars versus terrorism and other forms of political violence would be useful. Anjali Thomas Bohlken
and Ernest Sergenti (2008) document the close link
between local economic conditions and the outbreak
of communal (inter-religious) riots across Indian states. Blattman and Miguel: Civil War 7 0.4 –
95% upper band
95% lower band Incidence of civil war 0.3 – 0.2 – 0.1 – – – – – – – 0–
0 0.2 0.4 0.6 0.8 1 GDP per capita
Figure 3: Incidence of Civil War by Country Income per Capita, 1960–2006
Sources: Figure displays the results of a Fan regression of the incidence of civil war on GDP per capita
percentiles (bandwidth = 0.3, bootstrapped standard errors). Population and GDP data are drawn from
the World Development Indicators (World Bank 2008). Civil war incidence is drawn from the UCDP/PRIO
armed conflict database (Gleditsch et al. 2002; Harbom and Wallensteen 2007). Central theoretical problems remain
nresolved, including the sources of armed
group cohesion amid pervasive collective
action problems. Moreover, we have yet
to develop persuasive arguments for nontraditional mechanisms—myopic or selfish
leaders, for example, or the role of ideology
and identity in reducing free-riding within
armed groups. As a consequence, too little
empirical work is motivated by (and explicitly
derived from) formal models.
Second, the leading existing theories
remain untested. Simple contest models—ones that link conflict to geographic
onditions that favor insurgency, or ones
where poverty triggers political violence—
have been tested often. Yet one of the most dominant rational explanations for civil war,
conflict as the result of commitment problems that prevent socially desirable agreements between fighting sides, has barely
Third, theories seldom specify the empirical predictions that can test between competing accounts. What, for instance, is the
alternative to purely rational theories of warfare? “Irrational” warfare? In fact, there are
several plausible alternatives: rational actors
who do not internalize the social costs of war;
maximizing actors with systematic defects
in decision making or expectations formation; strategic interactions between multiple
actors within coalitions; idiosyncratic war
(described below); and so forth. Theory will 8 Journal of Economic Literature, Vol. XLVIII (March 2010) lead to better empirical testing if and when
it better specifies the empirical predictions
that distinguish between models.
Fourth, further cross-country regressions will only be useful if they distinguish
between competing explanations using more
credible econometric methods for establishing causality. Up to now this literature has
been enormously provocative but has faced
equally important limitations: convincing
causal identification of key relationships is
rare; robustness to alternative specifications
or assumptions is seldom explored; countryyears are often assumed to be independent
units in time and space; measurement error
is rarely addressed; an absence of evidence
about particular effects has often been interpreted as evidence of absence; and theories
of individual or armed group behavior are
tested at the country level despite obvious
aggregation difficulties. It would be easy to
conclude that the cross-country literature has
been exhausted, but that would go too far.
We highlight new macro-level research that
addresses some of these challenges head on.
Fifth, we believe the most promising
avenue for new empirical research is on the
subnational scale, analyzing conflict causes,
conduct, and consequences at the level of
armed groups, communities, and individuals. We refer mainly to the blossoming number of microeconomic statistical studies of
armed conflict and combatants, as well as
to the integration of quantitative evidence
with case and historical analysis. The empirical microeconomic work sometimes employs
more credible research designs, yet so far
the results are scattered and many findings
may be context-dependent. More studies are
exactly what is needed. In our view, the most
interesting directions for research include
the internal organization of armed groups,
rebel governance of civilians, the strategic
use of violence, counterinsurgency strategy,
and the roots of individual participation in
violent collective action. Each is ripe for the concerted application of contract theory and
mechanism design and insights from behavioral economics and industrial organization.
Sixth, we argue that researchers ought to
take a more systematic approach to understanding war’s economic consequences. An
episode of civil conflict, not its absence, is
the norm in most countries, and that war
may be a nation’s most important historical event. Yet what those effects imply for
long-run economic development is unclear.
This article also attempts to bring a unifying growth theory framework to the study of
war’s economic legacies. The bulk of existing
evidence focuses on war’s impacts on factors
of roduction—population and capital—and
finds that rapid recovery along these dimensions is possible. War’s impacts on human
capital (including education, nutrition, and
health), however, are often more persistent.
Like the “causes” literature, research into
“consequences” is beginning to benefit from
better micro-level data and greater use of
experimental or quasi-experimental variation. Viewed through the lens of economic
growth theory, however, there remain more
gaps than solid conclusions in our understanding of postwar recovery. Both theory
and evidence are weakest in assessing the
impact of civil war on the fundamental drivers of long-run economic performance—
institutions, technology, and culture—even
though these may govern whether a society
recovers, stagnates, or plunges back into war.
Finally, in pursuit of all these objectives,
much is to be gained from collecting new
data. We conclude our review with recent
examples and priorities for data development.
We share a title with a useful recent survey
by Collier and Anke Hoeffler (2007) but have
different goals. Collier and Hoeffler focus
n-depth on a set of core macroeconomic
questions. Our piece brings in a broader
range of research questions and approaches,
including an overview of the large conflict
literature in political science, and a critical Blattman and Miguel: Civil War
but hopeful view of the new applied microeconomic work in conflict, probably the single most promising research frontier in our
view. We also focus on the theoretical and
econometric limitations of existing work. We
believe a number of the arguments in this
article are novel or have never before been
assembled in a single place, including the
discussion of specific directions for future
The rest of the paper is organized as follows. On civil war causes, section 2 surveys
theoretical advances and section 3 covers the
large empirical literature. Section 4 tackles
the growing literature on civil war’s economic
consequences. The final section ummarizes
key lessons and policy implications, and suggests strategies to sustain intellectual progress in this emerging field.
2. Theories of Armed Conflict
Newspaper reports, historical accounts,
and econometric work overflow with
xplanations for conflict: ancient hatreds
incite violence; oil wealth breeds separatism; trade shocks trigger insurrections;
income inequality leads to class warfare.
Surveying the vast literature on civil war,
one feels caught in a complex web of root
and proximate causes (not to mention endogeneity). In this context, the principal contribution of formal economic theory has
been to clarify and systematize this tangle
of material explanations. Models from
both economics and political science have
reduced varied accounts of civil war onset
to a few common logics, each of which can
be approximated in a parsimonious framework of self-interested, wealth-maximizing
groups or individuals. We first review the
seminal theories of civil war, then other
influential branches of the theoretical literature, and wrap up this section with our
views on promising directions. 9 2.1 Insurrection as Competition for
Models of armed conflict depart from the
assumptions of standard economic theory
in at least three ways: property rights are
neither well-defined nor automatically protected, contracts between parties cannot
be enforced, and rulers can be replaced by
means other than the ballot box. In this lawless setting, predation and defense are alternatives to directly productive activities.
The contest model, the workhorse of the
formal conflict literature, originated with
Trygve Haavelmo (1954), and was popularized by Jack Hirshleifer (1988; 1989),
Michelle R. Garfinkel (1990), and Stergios
Skaperdas (1992). It considers two ompeting
parties, a rebel group and a government, and
analyzes each side’s allocation of resources to
production versus appropriation; Garfinkel
and Skaperdas (2007) summarize the permutations and mechanics of two-party contest
models embedded in a general equilibrium
framework. While production is modeled
in the standard manner, appropriation is
modeled using a “contest success function”
where inputs (e.g., guns, G) translate into
a probability of fighting side 1 winning, p1,
and consuming the opponent (side 2’s) economic production in addition to their own.
Following Hirshleifer (1989), the most commonly used formulation in theoreticalapplications is presented in equation 1, where G1
refers to side 1’s weapons, G2 refers to 2’s
weapons, and m captures the effectiveness of
weaponry in determining the victor: (1) m
p1 (G1, G2) = ________ .
G1 + G2 Contest models boast at least one robust
prediction: the odds of winning increase
with the relative effectiveness of that side’s 10 Journal of Economic Literature, Vol. XLVIII (March 2010) fighting technology. Technology is defined
broadly in this literature, including any factor that influences effectiveness, from skillful
revolutionary leaders, to access to firearms
and training, rugged terrain, or bases on foreign soil. As we will see below, this prediction receives broad empirical support in the
success of rebel movements, contributing to
the popularity of the contest approach.
Contest models often treat rebels and rulers as unitary actors. Hershel I. Grossman
(1991) departs slightly, considering the case
of a single ruler and many citizens, each
of whom can either produce or predate.5
Grossman’s move from unitary actors to
epresentative households (assumed unable
to coordinate their activities) does not greatly
change the conclusions of the contest model,
but it does highlight the importance of the
individual participation problem: armed
group leaders must motivate citizens to soldier for their side. One immediate insight is
that participation in soldiering rises as the
opportunity cost of fighting falls.
These models thus predict that poverty
lowers individual incentives for maintaining
order, as soldiering increases with the relative returns to fighting versus production.
Can this prediction account for the crosscountry correlation between poverty and
civil war? In fact, the theoretical connection
between income and armed civil conflict is
not so clear cut. In contest models the winning party consumes the resources of both
the state and the losers. On the one hand,
the greater the national wealth (whether
from taxes, assets like natural resources, or
external transfers), the more there is to fight
over and thus, in standard formulations, the
greater the quilibrium effort devoted to
fighting rather than producing (e.g., Garfinkel
and Skaperdas 2007; Grossman 1999). Yet the absence of resources—natural or otherwise—makes production less individually
attractive than fighting, but also means there
is a smaller pie to fight over. James D. Fearon
(2007) notes that these opposing wealth
effects cancel out in some cases: if state revenues are drawn entirely from taxes on citizen
incomes, then income could have no effect
on equilibrium levels of conflict. Positive or
negative income effects could result, though,
if utility or revenue collection has a nonlinear
Ernesto Dal Bó and Pedro Dal Bó (2004)
model these potentially opposing effects in
a two-sector model of the economy. In the
capital-intensive sector, an income shock
increases the value of controlling the state
without increasing wages and the opportunity cost of fighting; the opposite is true of
a shock to the labor-intensive sector. Thus
in the first case conflict risk increases, while
in the second it falls. Timothy J. Besley and
Torsten Persson (2008a; forthcoming) use
a related framework to model the impact
of import and export commodity prices
on government revenues and rents, as well
as on labor incomes. They conclude that
terms of trade volatility in either direction
may timulate repression and armed cons
flict: increasing import prices increase conflict risk by suppressing the real wage while
higher export prices lead to greater conflict
risk by boosting the size of the government
revenue pie tempting armed groups. A notable aspect is the authors’ attempt to link
these sharp theoretical predictions to crosscountry evidence, and we return to their
empirical findings below. Both papers also
suggest that the distribution of income and
wealth—whether across individuals or sectors—is central in explaining the economic
ncentives for ebellion.6 Civil war seems
r 5 Another approach considers a rebel leader who competes with the incumbent for citizen support (Grossman
1999). 6 See Roland Benabou (2000) and Abhijit V. Banerjee
and Esther Duflo (2003) on inequality and economic performance across countries. Blattman and Miguel: Civil War
more likely when state wealth is easily appropriated or divorced from the citizenry, as
with some natural resource wealth and foreign aid flows. We revisit this issue below.
2.2 Why Fight? Information Asymmetry
and Incomplete Contracting
One drawback of the typical contest model
is that insurrection is never fully deterred;
arming and fighting always occur in equilibrium. There is typically no decision to fight:
arming and fighting are one and the same.
This prediction of ever-present conflict is
unsatisfying since political competition over
power and resources is ubiquitous while violent conflict is not. Thus we turn to the determinants of compromise (and its breakdown).
Creating and arming organizations is
costly and wars are destructive and risky.
Thus a fundamental question is why wars
ever occur at all. If the competing groups are
rational, both should prefer a bargained solution to destructive conflict.
The possibility of bargaining under the
threat of violence is embedded in leading
theories of political and institutional development.7 Acemoglu and Robinson (2001, 2006),
for instance, develop a model of elites competing with the poor for control of the state.
Elites accommodate the poor by extending
the voting franchise in periods when the poor
can credibly threaten to revolt, and there is
no violent conflict on the equilibrium path.
Carles Boix (2003) develops a related model,
where conflict outbreaks depend on shifts
in the military capacity of a evolutionary
7 Bargaining models of conflict proceed from micro- economic theories of bargaining where parties have the
option of resorting to costly conflict if bargaining breaks
down (see John Kennan and Robert Wilson 1993 for a
comprehensive survey). Union–firm wage negotiation and
pretrial legal settlement in wealthy countries have been
the two most studied cases. Conflict models, however, do
not assume that contracts will be enforced once signed,
further complicating the negotiation. Barry R. Posen
(1993) presents a theoretical international relations perspective on ethnic conflict. 11 c
hallenger. Fearon (1995) famously outlined
three reasons why bargaining could fail, leading to inter-state war. First, leaders may not
always behave rationally—decisions might
be based on emotion, or leaders may not fully
calculate benefits and risks (bounded rationality). Second, leaders may be fully rational
but not internalize the full cost of conflict
because of political agency problems. Third,
leaders might be rational and internalize
costs, but find war unavoidable nonetheless.
Almost all theoretical work focuses on
this third case. Fearon highlights three
mechanisms consistent with “rational war”:
(i) asymmetric information, including private information about military strength,
and the strategic incentive to misrepresent
it to potential opponents;8 (ii) commitment
problems, especially the inability of the parties to commit to deals in the absence of a
third-party enforcer; and (iii) issue indivisibilities, whereby some issues do not admit
ompromise. We will follow the literature
and focus attention on the first two.9
2.2.1 Information Asymmetries
War can occur when one side overestimates its ability to win, or underestimates
its opponent’s strength (Powell 2002). But
asymmetric information is generally insufficient cause for war. After all, if both arties
have an incentive to make a deal, they should
also have incentives to gather information
and communicate their strengths (Fearon
1995). For asymmetries to cause war among
8 This argument appears to originate with Dagobert L.
Brito and Michael D. Intriligator (1985).
9 Issue indivisibilities are considered a relatively minor
explanation in most cases. However, Ron E. Hassner
(2003) argues that the indivisibility of sacred spaces may
be one reason for the persistence of conflict between
Israelis and Palestinians or Hindus and Muslims in India.
Robert Powell (2006) argues, however, that indivisibilities
are merely a special case of the commitment problem; if
commitment were possible, both sides would prefer a lottery that awards the contested indivisible prize with the
same odds as fighting, thus avoiding war’s destruction. 12 Journal of Economic Literature, Vol. XLVIII (March 2010) r
ational actors, accurate disclosure of information must also be impaired. An incentive to
misrepresent one’s strength is the most commonly theorized mechanism, such as when
a state exaggerates its strength and engages
in (inefficient) war in order to deter future
opponents from insurrection.10 To take an
interstate war case as an example, Saddam
Hussein’s exaggeration of Iraq’s stock of weapons of mass destruction in 2002 could be seen
as an effort to mislead opponents and deter
invasion—an effort that, nevertheless, failed.
Such accounts are plausible but likely offer
only half an explanation. For one, relative
military strength should reveal itself quickly
on the battlefield. Information problems thus
provide a particularly poor account of the
many prolonged civil conflicts (Fearon 2004;
Most models also assume just two actors.
Civil wars are seldom so simple. Joan Esteban
and Ray (2001) develop a multiplayer contest, where each has imperfect information
about the others’ costs of conflict. With four
or more players, Pareto-improving social
decision making is impossible and conflict
ensues. Thus information asymmetries may
be even more hazardous than the basic twoplayer models would suggest. Ray (2009)
identifies another rational route to conflict
when players are many, developing a model
of coalition formation under multiple threats
that shows that conflict may be unavoidable
even in a world with complete contracts.
Societies divide along multiple lines—by
class, geography, religion, or ethnicity—and
while society can arrange a set of transfers
10 For instance, Barbara F. Walter (2006) shows that
ethnic groups are more likely to seek self-determination
if a government has acquiesced to earlier autonomy
demands by other groups. A government that takes such
future externalities into account might find it worthwhile
to fight a costly war today to prevent secession, thus possibly heading off future conflicts. The relationship also
suggests that war may not always be accurately modeled
as a two-player game. that avoids a conflict along any one division,
it may be impossible to find an arrangement
that simultaneously prevents conflicts along
all divisions simultaneously.11
Also promising are recent attempts to integrate asymmetric information with other
theoretical mechanisms. Sylvain Chassang
and Gerard Padro-i-Miquel’s (2008a, 2008b,
2009) work incorporates such asymmetry
into a contest model employing a global
games logic.12 Their key insight is that transient economic shocks increase the immediate ncentives to fight but not the discounted
present value of victory. The model thus
implies that in dire economic circumstances
groups predate upon one another since they
have less to lose than in periods where the
returns to production are higher. Yet conflict is also possible in better economic
times as asymmetric information on the true
economic conditions, and first-strike advantages on the battlefield, combine to generate mutual fears of preemptive attacks. The
framework is notable for its testable predictions: armed conflicts should follow negative
economic shocks; higher and less volatile
national incomes are associated with less
conflict; and expected future income growth
reduces the risk of war today.13
11 Motivated by warlord politics in Tajikistan and
Georgia, Jesse Driscoll (2008) models bargaining between
a president and multiple challengers.
12 Global games are associated with the work of Hans
Carlsson and Eric van Damme (1993) and Stephen Morris
and Hyun Song Shin (1998).
13 Chassang and Padro-i-Miquel show that there are
always economic conditions severe enough that civil conflict breaks out. In their notation, the size of the national
economic pie in period t is θt ∈ (0, ∞); c is the fraction of
production destroyed in a civil war; P is the odds that a
fighting side will prevail if conflict breaks out; V V is the
continuation value if that side prevails in the war; VP is the
continuation value of the most peaceful Subgame Perfect
Nash Equilibrium; and δ is the time discount rate. They
show that peace is only sustainable if θt [1 − 2 P(1 − c)] ≥
δ [PV V − VP ]. Since the right hand side of the expression
is strictly positive for plausible parameter values, there is
always an economic shock sufficiently bad (close to zero)
that violates this inequality. Blattman and Miguel: Civil War
Dal Bó and Powell (2009) also show that
asymmetric information can lead to war in
the context of pervasive commitment problems without relying on global games. The
government has better information on its
wealth than challengers. As in Chassang and
Padro-i-Miquel, they show that government
attempts to buy off the opposition (and avoid
conflict by offering them a share of the pie)
fail in periods of lower economic activity,
since the challenger fears that the government is low-balling them. Commitment problems could further restrict the government’s
ability to secure peace by incorporating the
challenger into a power-sharing government
(since this would provide the challenger with
a stronger position for future aggression).
Sandeep Baliga and Tomas Sjostrom (2004)
develop a related imperfect commitment
model, in which private information about
each fighting side’s propensity to arm can
lead to arms races with probability close to
2.2.2 Commitment Problems and
The most intriguing theories of civil war
focus on the cases where credible commitments to peace or redistribution cannot be
made even with complete information—
that is, at least one side faces an incentive to
renege once a settlement is reached (Walter
1997). Such circumstances include military
scenarios with a first-strike advantage, and
instances where waging war today can prevent one’s opponent from gaining military
strength in the future.
Powell (2006) shows formally that each
of these commitment problems is rooted
in a single phenomenon: large shifts in the
future distribution of power. For a leading
example, consider a temporarily weak government that is attempting to “buy off ” a
strong rebel group with transfers to secure
peace. When the state returns to relative 13 strength— erhaps because of a rebound
in economic activity, foreign aid or commodity revenues—it will be tempted to
renege on its earlier bargain, thus limiting
the amount it can credibly promise to the
rebel group today. If this time-consistent
but more modest transfer is less than what
the rebels can gain by fighting today, they
will wage war now to lock in the highest
Similarly, a commitment problem arises
when one party can permanently alter
the strategic balance of power by waging
war now (Garfinkel and Skaperdas 2000;
Michael McBride and Skaperdas 2007;
Powell 2006). If going to war weakens or
even eliminates a rebel group for all time,
the state will gain a peace dividend since it
no longer needs to spend on arms to deter
future conflict. Thus the state has reason
to wage bloody but short conflicts if peace
deals are not credible.14
The commitment problem directly suggests that civil war is more likely to occur
when there are limits to conflict resolution
and contract enforcement. Since formal legal
and state institutions presumably help to
enforce commitments intertemporally, societies with weak government institutions and
few checks and balances on executive power
should empirically be those most likely to
experience violent civil conflict (e.g., Fearon
and Laitin 2003; Eliana La Ferrara and
Robert H. Bates 2001; Skaperdas 2008). This 14 This approach suggests that the likelihood of war
is affected by each side’s valuation of the future versus
the present. The risk of future retaliation—the “shadow
of the future”—should deter sides from conflict. When
future returns depend on present success on the battlefield, however (i.e., first-strike advantages), the shadow
the future can increase the incentives for conflict. It can
also lead to war if a peace settlement is costly in terms of
expected future defensive arming. Greater intertemporal
discounting increases the likelihood of war in the first case
and decreases it in the second and third (McBride and
Skaperdas 2007; Skaperdas and Constantinos Syropoulos
1996). 14 Journal of Economic Literature, Vol. XLVIII (March 2010) relationship may partially explain the widespread occurrence of lengthy civil wars in
sub-Saharan Africa, a region notorious for its
weak state capacity and limited legal infrastructure (Bates 2001; Bates 2008; Jeffrey
Yet weak institutions and the absence of a
third-party enforcer alone are not sufficient
cause for civil conflict. The theory implies
that conflict is at least twice conditional: first
on weak institutions, and second, on future
shifts in relative power across the fighting
sides. Future empirical models must begin
to take these issues into account more seriously in testing.
In terms of policy, the theory suggests
that enforcement of contracts by the international community can potentially substitute for weak domestic institutions (Walter
1997). Interventions might include armed
peacekeepers, the provision of guaranteed
financial transfers to rebels by outside international agencies, and the threat of punishment (including trade sanctions, asset
freezes, and bombing) if either side reneges
on the peace deal.
External interventions could also have
the opposite effect, however, and prevent an
ongoing war from reaching a credible peace
agreement. For instance, the recent prosecution of Charles Taylor (former warlord
and President of Liberia) and indictment
of Joseph Kony (head of Uganda’s Lord’s
Resistance Army) by international courts
could make postwar power-sharing deals for
rebels less credible in the future, and thus
extend current civil wars if the rebels have
no guarantee that putting down arms will
shield them from prosecution in The Hague.
On the other hand, the possibility that an
international indictment could be dropped
appears to have been one of the primary
incentives for Kony to agree to a ceasefire and
begin negotiating peace in the first place. We
discuss the scattered empirical evidence on
international interventions below. 2.3 The Microfoundations of Group
Contest models and rationalist theories
of civil war rely upon groups behaving as
unitary actors, strong assumptions considering the well-known problem of collective
action (Mancur Olson 1971). To understand
the causes of war, we must also understand
how groups form, cohere, and persuade their
members to risk their lives.
2.3.1 Civil War and the Participation
Classic solutions to the collective action
problem use “selective incentives” to motivate participation, with material and pecuniary incentives the focus of most models (e.g.,
Grossman 1999). Such incentives include
wages, opportunities to loot, promises of
future reward, or physical protection from
harm. Economic inequality provides a possible motive for conflict to the extent that
eizure of the state brings material gains to
the victors (Fearon 2007).
A literature on agrarian revolutions in the
1960s and 1970s argues instead that inequality motivates participation in rebellion not
for private gain, but because it generates
frustration over inequality or the destabilization of traditional social systems (James C.
Davies 1962; Ted Robert Gurr 1971; Jeffery
M. Paige 1975; Roger D. Petersen 2001;
James C. Scott 1976). By these accounts,
poverty, income inequality, and unmet economic expectations may indeed be the root
causes of conflict, but the more proximate
explanations are better described as grievances. Rather than deny material motivations, these accounts provide an alternative
set of mechanisms for individual participation in rebellion.
Related nonmaterial incentives are thought
to be common within armed groups. Several
studies argue that a leader’s charisma, group
ideology, or a citizen’s satisfaction in pursuing Blattman and Miguel: Civil War
justice (or vengeance) can also help solve the
problem of collective action in rebellion (e.g.,
John E. Roemer 1985; Elisabeth Jean Wood
2003b). These unconventional incentives
have typically been the subject of sociology
(Amitai Etzioni 1975; Olson 1971). A convenient way of modeling such sentiments in a
rational framework is as “goods” of inherent
value that individuals consume by fighting.15
What these micro-level approaches often
ignore, however, is that fighting is not the
only means by which individuals and groups
can pursue political and economic change.
Walter (2004) argues that the absence of
a nonviolent means for achieving change
is also often necessary to incite rebellion.
Nonviolent political alternatives could be
incorporated into the decision framework
facing citizens, leaders, and armed groups,
generating testable predictions about the
relationship between political institutions
and the likelihood of civil conflict.16
Such diverse selective incentives—pecuniary or not—are easily embedded in a principal–agent framework. A leading example is
Scott Gates (2002), who models how rebel
leaders can use material incentives alongside ethnic appeals to motivate citizens to
join and exert effort in the rebellion (i.e., to
satisfy the participation and incentive compatibility constraints). His model emphasizes
how incentives and methods of recruitment
vary with ease of supervision; the greater the
distance—whether geographic or social—
between the leader and the recruit, the more
15 The approach closely parallels two literatures. One
is a branch of the voting literature that suggests the collective action problem inherent in participation in democratic elections (where the odds of affecting the outcome
are infinitesimal but voting has concrete costs) is overcome
by the value some individuals place on the act of voting
itself (Amrita Dhillon and Susana Peralta 2002; Timothy
J. Feddersen 2004). A literature on revolution emphasizes
the inherent value individuals place on retaliation against
an unjust state (Frantz Fanon 1961).
16 Matthew Ellman and Leonard Wantchekon (2000) is
a useful step in this direction. 15 difficult are supervision and punishment, and
the more likely that material incentives (e.g.,
looting) will need to be offered to recruits to
secure their cooperation.
Threats and punishments can also be used
as selective incentives. Coercive recruitment
is especially common in African insurgencies where, in the absence of a shared social
basis for mobilizing rural support, rebel leaders resort to the only tool at their disposal
(Thandika Mkandawire 2002). Michael SukYoung Chwe (1990) and Bernd Beber and
Christopher Blattman (2008) model the use of
coercion and pain in a principal-agent setting,
and identify the conditions (and agent types)
where it is optimal for armed group leaders
to threaten pain instead of offering rewards.
This consumption approach to nonpecuniary
incentives is analytically onvenient and yields
useful insights, such as the rationale for using
coercion on low productivity recruits (especially children). Yet these models are unlikely
to capture the complex individual motivations
underlying participation in armed groups,
however, and thus constitute an important
area for further research.
2.3.2 The Formation of Competing
The models reviewed assume that rebel
and government groups exist and are actively
engaged in combat. They do not tackle the
issue of how competing groups form and why
they cohere. An emerging literature based
on the noncooperative theory of endogenous
coalitions explores the distributional basis
of group formation. These models typically
assume that group action is more efficient
than individual action, providing citizens
with an incentive to join forces. These models also allow for conflict within each group
over the distribution of their joint surplus,
conflict that can be costly for the individual. Stable groups are those that have lowcost mechanisms for distributing the gains,
such as property rights norms. The size of 16 Journal of Economic Literature, Vol. XLVIII (March 2010) stable groups depends on the relative effectiveness of groups at managing both intergroup and intra-group conflict (e.g., Francis
Bloch, Sántiago Sánchez-Pagés, and Raphael
Soubeyran 2006; Garfinkel 2004). This
approach is a promising source of microfoundations for the commitment problems
discussed above, since the institutions that
allow for within-group cooperation may also
mitigate intergroup conflict.
Relaxing the unitary actor assumption
could also expand the range of rational
explanations for armed conflict. Information
problems within groups could lead to bargaining breakdowns (just as was the case for
asymmetric information across groups). Field
generals have incentives to mislead civilian
leaders about the capability of their military
forces if they hope to keep the fighting going
for longer than citizens would like (to keep
military budgets at high levels, for instance).
Alternatively, the possibility that groups
might split could exacerbate commitment
problems: signing a peace deal with a rebel
group leader is of limited value if hard-liners
are able to secede and continue fighting.17 The
existence of splinter factions may explain the
reluctance of fighting sides to enter into peace
talks and cause such talks to fail. Stephen
John Stedman (1997) argues that the greatest
risk for peace negotiations comes from such
“spoilers”: “leaders and parties who believe
that peace emerging from negotiations threatens their power, worldview, and interests, and
use violence to undermine attempts to achieve
it” (p. 5). Ray (2007; 2009) and Acemoglu,
Georgy Egorov, and Konstantin Sonin (2009)
discuss coalitional stability when such deviations and counterdeviations can occur.
17 For example, Stathis N. Kalyvas (2000) argues that
internal divisions between moderates and radicals within
Algeria’s Islamist FIS party, and the moderates’ inability
to make binding policy commitments to reassure antiIslamist elements of the national army, contributed to the
outbreak of civil war there after FIS won the 1991 national
election. 2.3.3 Ethnic Groups and Conflict
Ethnic nationalism is popularly viewed as
the leading source of group cohesion and (by
extension) intergroup civil conflict; of 709
minority ethnic groups identified around the
world, at least 100 had members engage in an
ethnically based rebellion against the state
during 1945 to 1998 (Fearon 2006). But why
do ethnic groups themselves form, cohere,
and sometimes engage in such violence? A
full review of the literature on the formation
of ethnicity and ethnic conflict is beyond
the scope of this paper, but an outline of the
main ideas merits discussion.18
“Primordialist” arguments stress the
deep cultural, biological or psychological
nature of ethnic cleavages, whereby conflict is rooted in intense emotional reactions and feelings of mutual threat (Donald
L. Horowitz 1985). Economic models that
assume individuals prefer to mingle with
co-ethnics (or share political preferences)
might be construed as primordialist in
nature (Alesina, Reza Baqir, and William
Easterly 1999; Alesina and La Ferrara 2000;
Esteban and Ray 1999). There are clear
parallels to the models of group formation
discussed above: co-ethnic preferences can
augment intragroup mechanisms of communication and cooperation, while interethnic
animosities may exacerbate information and
commitment problems.19 18 For overviews of ethnic mobilization and violence
see Laitin (2007), Fearon (2006), and Bates (2008). On
ethnic divisions and economic performance, see Alberto
Alesina and La Ferrara (2005) and Pranab Bardhan (1997;
19 Alternatively, as with the grievances discussed above,
ethnic violence might have inherent utility value. In the
extreme case, we could even reject the rationalist assumption entirely that opposing ethnic groups prefer to reach a
peaceful solution. However, we believe the goals of formal
economic theory here should go beyond simply assuming
that a taste for violence drives civil conflict, to uncover the
deeper economic, political and social factors at play. Blattman and Miguel: Civil War
Even if ethnic identities are not primordial
and inter-ethnic animosities are absent, ethnicity may still facilitate strategic coordination
and enforcement. Ethnic groups often exhibit
dense social networks and low cost information and sanctioning, and may have identifiable characteristics that allow outsiders to
be excluded from public goods (Francesco
Caselli and Wilbur John Coleman 2006;
Fearon and Laitin 1996; Edward Miguel
and Mary Kay Gugerty 2005). Fearon and
Laitin (1996) show that better within-group
cohesion can facilitate peace deals between
ethnic groups. Alesina and La Ferrara (2005)
also speculate that ethnically homogenous
groups possess a production advantage that
augments their incentives to associate. Bates
(1986) argues that shared language and customs facilitate organization. Finally, Esteban
and Ray (2008) suggest that ethnic alliances
have a distinct advantage over class alliances in mobilizing for conflict. While class
and ethnic groups both possess shared social
identities, only ethnic groups exhibit withingroup economic inequality: inequality allows
the rich to supply conflict capital (e.g., guns)
while the poor supply conflict labor.
Finally, “modernist” theories stress that
ethnic conflict arises when groups excluded
from social and political power begin to
experience economic modernization (Bates
1986; Ernest Gellner 1983)—a situation that
parallels Powell’s (2006) account of shifts in
future power leading to bargaining breakdowns today.
2.4 Challenges and Areas for Further Work
Most real-world disputes are settled, even
among antagonistic ethnic groups. Thus the
theoretical apparatus described above is
plausible: conflict is rooted in endemic competition for resources across groups, with
bargained solutions occasionally breaking
down because of commitment or information
problems. Persuasive though this framework
may be in many circumstances, there remain 17 many challenges and areas for further theoretical investigation.
2.4.1 Disentangling Competing Accounts
Existing formal theories of conflict yield
falsifiable predictions, but few articulate the
precise empirical tests that would distinguish
among alternative mechanisms. Income
volatility is one example. In the theories we
consider above, a negative aggregate income
shock is associated with an increase in armed
conflict in various models, including those
that emphasize the diminished opportunity
costs of soldiering (Gates 2002, Chassang and
Padro-i-Miquel 2009), weaker state repressive capacity (Fearon and Laitin 2003), or the
role of asymmetric information (Chassang
and Padro-i-Miquel 2008a). Meanwhile, a
negative aggregate income shock is associated
with a decrease in conflict risk in models that
stress capturing the state and its revenues as
a prize (e.g., Garfinkel and Skaperdas 2007;
Grossman 1999). Finally, income volatility in either direction could inhibit credible
bargaining and commitments if it is associated with rapid shifts in power across groups
(Powell 2006), or gives rise to worse information about current economic conditions (Dal
Bó and Powell 2009). Few theories model
more than one of these dynamics or identify
the empirical predictions that will adjudicate
among competing accounts.
One exception is Dal Bó and Dal Bó (2004),
who distinguish between shocks to different
economic sectors. This theory is an improvement over single-sector models, yet even so,
alternative mechanisms and interpretations
are still possible. For instance, if higher capital-intensive good prices fail to increase conflict, it might be because greater state capacity
(associated with higher government revenue)
dominates the state-as-prize effect. If civil
war is the result of a bargaining breakdown,
there are good theoretical reasons to believe
that events such as price shocks have differential effects on civil onflict depending on
c 18 Journal of Economic Literature, Vol. XLVIII (March 2010) the local institutional setting, the number of
already existing armed groups, and the future
shifts in power across political groups likely
to result. Future theoretical work should follow the lead of this paper in helping us pinpoint the empirical patterns that distinguish
between alternative mechanisms.
2.4.2 Understanding Grievances
At present, the economic motivations for
conflict are better theorized than psychological
or sociological factors. Individual preferences
in existing models typically include only material rewards and punishments. One implication is that we have not derived the falsifiable
predictions that distinguish between material
and on-material heoretical accounts. Thus
we cannot discard non-economic explanations for conflict. Take the role of economic
inequality, for example. The unequal distribution of resources can generate material
incentives for a relatively poor group to seize
control of the state. More than one historical
account, however, emphasizes citizens’ emotional and ideological outrage over inequality
as a prime motivation for engaging in violent
collective action.20 While the reduced-form
prediction that greater economic nequality
leads to armed conflict is unchanged in either
case, the relationship could be nterpreted as
evidence of either “greed” (economic motivations) or “grievance.”
Christopher Cramer (2002) critiques the
conflict literature for its tendency to use such
reduced-form empirical relationships to buttress economic interpretations, arguing that
the underlying relationships between economic, social, and psychological factors are far
more complex. He stresses Antonio Gramsci’s
(1971) definition of “economism”: presenting
20 Barrington Moore (1993), for instance, has argued
that Nazi fascism and anticapitalist rhetoric stirred
anger in German peasants over the perceived control of
resources by a supposedly hostile Jewish elite. A similar
dynamic was at work during the anti-Tutsi genocide in
Rwanda in 1994 (Scott Straus 2006). causes as immediately operative that in fact
only operate indirectly, and thus overstating
proximate causation. Understanding these
complex relationships is crucially important
for preventing armed conflicts. Innovative
ways of modeling and measuring individual
political grievances are required to make
progress on this agenda. Yet in the end, our
measures may fail to capture the relevant variation. Grievances are fluid and the case literature points to the evolution of identities and
norms during wartime (Wood 2003a).
Recent behavioral and experimental economic research argues that notions of fairness
and grievance are salient in individual decision making. There is growing lab evidence
that individuals have a taste for punishing
social norms violations and are willing to
incur nontrivial private costs to do so. This
willingness to punish unfair behavior appears
to have neural-physiological underpinnings
(Dominique J.-F. de Quervain et al. 2004) and
is consistent with preferences for equity (Gary
Charness and Matthew Rabin 2002; Ernst
Fehr and Klaus M. Schmidt 1999). Jung-Kyoo
Choi and Samuel Bowles (2007) argue that
altruistic preferences favoring one’s in-group
may have conferred an evolutionary advantage. Such within-group social preferences
could reduce the local collective action problem inherent in mobilizing armed groups by
lowering the cost of sanctioning free riders.21
21 The taste for violence may differ from the taste for
punishing others monetarily, but the experimental economics literature has not to our knowledge carried out
similar research on individual preferences for inflicting
violence on others. Given the inherent human subjects
issues, observational data on perpetrators of violence is
a more promising avenue here. Sociological and psychological understandings of interpersonal violence contrasts
sharply with the rational choice approach we emphasize in
this article. Sociologist Randall Collins (2008) argues that
most interpersonal and combat violence is characterized
by a short and confused belligerent “haze”: actors are emotionally overwhelmed with tension and fear, and violence
is perceived as the resolution of this fear. Meanwhile,
some public health and psychology evidence suggests that
much violence is “shame-induced” (James Gilligan 2000). Blattman and Miguel: Civil War
2.4.3 Disaggregating Institutions
The commitment problem is a persuasive
explanation for civil war. Unfortunately, we
have a poor understanding of the specific
political and legal institutions capable of
enforcing commitments and facilitating compromise between competing groups. Some
theories emphasize the importance of market promotion and tax levying (Besley and
Persson 2008b), and others property rights
and the rule of law (Garfinkel 2004). Still
others emphasize the role of international
institutions and the threat of external intervention, others the internal legitimacy of
the state (e.g., the rule of a minority ethnic
group, whether in Tutsi Rwanda or apartheid
South Africa, could be particularly destabilizing). Meanwhile, Powell (2006) emphasizes institutions that help manage rapid
shifts in power, an example of which might
be the ability of elites to extend or retract
the democratic franchise, as in Acemoglu
and Robinson (2001, 2006). The “institutions” concept needs to be better disaggregated and tested to be useful in the civil war
Barry R. Weingast (1997), Bates (2008)
and Bates, Avner Greif and Smita Singh
(2002) argue that the incentives and constraints facing leaders are crucial, and in
particular that rulers loot the state when
the long-term costs of doing so are low.
Institutions shape these costs as well as
the ruler’s time horizon and discount rate.
Paradoxically, institutions that extend a
ruler’s horizon, such as the elimination of
term limits or the weakening of political
competition, may increase the incentives for
supporting political order, so the ruler can
extract rents over a longer time. Conversely,
Bates (2008) argues that international pressure for African states to democratize in
the 1990s increased disorder, since it shortened leaders’ horizons at the same time that
foreign aid flows were reduced; with few 19 institutional checks on their power, African
rulers had incentives to predate.
These arguments meld with a growing
comparative politics literature on state failure and “warlordism” in the late twentieth
century. In a study of civil war in Liberia,
Sierra Leone, and Guinea, Amos Sawyer
(2004, 2005) emphasizes the large spoils
from power combined with the absence
of checks and balances on the executive as
the primary cause of war in those nations.
William Reno (1999) also examines the internal dynamics of “warlord states” in Sierra
Leone, Nigeria, the Democratic Republic of
Congo, and Liberia. Like Bates, Reno argues
that, in the presence of resource wealth, a
weakened state, less foreign aid, and pressures for economic liberalization, strongmen
found it optimal to deinstitutionalize the
state and formal bureaucratic mechanisms in
favor of a parallel “shadow state” under their
2.4.4 The Conduct and Organization of
Another important area of study is the
conduct of rebellion, investigating what factors and initial conditions influence a group’s
formation, recruitment strategies, fighting
tactics, and internal organization. One goal
is to describe the logic of civil war and violence—a reaction to the view, popularized
by journalism and some international relations scholars, that the brutal violence that
haracterizes much of modern civil warfare is
a product of illogical barbarism unrestrained
by economic, political or social structures
(e.g., Mary Kaldor 1999; Robert D. Kaplan
Rebel groups are large, self-sustaining
indigenous organizations in societies where
effective organizations (including private
firms) are rare; understanding the glue that
holds them together should be a top research
priority. One strand of recent research applies
contract theory to theories of ecruitment.
r 20 Journal of Economic Literature, Vol. XLVIII (March 2010) Some of these, already discussed above, focus
on how armed groups motivate recruits to
fight (e.g., Beber and Blattman 2008; Gates
2002, 2004). Weinstein (2005b, 2007) develops a theory linking a rebel group’s social and
economic endowments to its composition and
tactics. He argues that groups rich in material resources are flooded with opportunistic
joiners with little commitment to the civilian
population, while armed organizations with
ideological “resources,” like a strong sense of
common identity, tend to attract more committed soldiers.22
Armed group cohesion is the subject of a
large body of work in military sociology and
history. Rather than focusing on economic
incentives, this literature emphasizes the
powerful role of group socialization and social
identity in generating solidarity, commitment,
and a willingness to risk one’s life (see Paul D.
Kenny 2008 for a review). Influential organizational devices include the creation of new
identities among recruits and unit solidarity (Richard A. Gabriel and Paul L. Savage
1979; Edward A. Shils and Morris Janowitz
1948) and systems of command and control
(Robert Sterling Rush 1999, 2001; Martin
Van Creveld 1982). This emphasis on organization-level dynamics in state militaries contrasts with the emphasis on individual-level
motives often used to explain participation in
nonstate groups; we believe both literatures
could gain from an exchange of perspectives.
Two such crossovers are Francisco Gutiérrez
Sanín (2008), who examines Colombian paramilitary and guerrilla groups, and Wood
(2008), who discusses how armed groups have
22 The contrast between the Revolutionary United
Front (RUF), funded through diamond mining and smuggling, and the community-supported Civilian Defense
Forces (CDF) in Sierra Leone’s recent civil war provides an illustration of this divergence. L. Alison Smith,
Catherine Gambette and Thomas Longley (2004) show
that the RUF was much more likely to commit human
rights abuses against civilians than the CDF. See David
Keen (2005) for a careful discussion of the Sierra Leone
civil war. constructed identities and reconfigured social
networks in El Salvador, Peru, Sierra Leone,
and Sri Lanka.
Fearon (2007) asks why we tend to see the
sustained survival of many small and lightlyarmed guerrilla groups, each with little
chance of capturing political power (Congo,
Sudan and Uganda are countries where this
has been true). He constructs a contest success function with decreasing returns to scale
for rebels over some size range—in other
words, above some size, each additional rebel
increases the probability the rebel group is
detected, denounced, or destroyed by the
government, and this effect outweighs the
fighting benefits of greater size (at least up to
some point).23 Powell (2007) is perhaps the
best articulated formal attempt to get inside
the black box of armed groups’ fighting strategies. He models optimal military spending
across potential targets (e.g., cities or fighting
units) by a government fearing rebel attack,
and is able to decompose such spending into
a defensive effect, a deterrence effect, and a
Finally, other models help to explain rebel
violence directed at civilians.24 Jean-Paul
Azam (2002, 2006) formalizes a strategic
logic whereby an armed group engages in
looting to reduce the returns to non-military
labor effort for potential recruits (thus making them more likely to join the group), while
simultaneously generating spoils to reward
existing recruits. The logic of violence
against civilian populations is the subject of
a growing literature in political science (see
Kalyvas 2006 for a review). In work based
on a comparative study of irregular civil
wars (i.e., guerrilla wars) in the past century,
Kalyvas (2006) argues that rival sides prefer 23 The sensitivity of results to such functional form
assumptions calls out for more research investigating the
micro-foundations of contest success functions.
24 See Straus (2007) for a review of the related literature on the perpetrators of violence. Blattman and Miguel: Civil War
to use selective rather than indiscriminate
violence to punish “defectors,” or civilian
enemies and informers. In the absence of
information, both sides rely on local collaborators to denounce defectors. Kalyvas argues
that selective violence—including violence
related to private, not political motives—is
most widespread in zones where each side
holds significant force but lacks full control.25
Finally, recent studies examine the use of
sexual violence by armed groups (Dara Kay
Cohen 2008; Wood 2006; 2009).
This collection of theories just scratches
the surface of the recruitment of fighters and organization of civil warfare. This
area remains one of the most promising
and understudied areas in the literature
on conflict, and is ripe for the application
of advances in contract theory, corporate
finance, behavioral economics and industrial
organization (Jean Tirole 1988, 2006). New
evidence to motivate and test these theories
is discussed in section 3.
2.4.5 Departures from the Rational Model
As we discuss below, existing empirical
models of conflict have limited explanatory and predictive power. We can draw at
least three possible conclusions from their
elatively weak performance. First, the
determinants of war could be understood
within standard rational choice frameworks
but simply difficult to measure. In this case
our prime focus as researchers should be to
improve data and measurement. To some
extent this is already happening.
Second, war could have idiosyncratic
causes, attributable to chance, singular circumstances, or unsystematic “irrational’
behaviors by leaders, encompassing errors
in decision making, personality defects,
25 In contrast, according to Kalyvas, the most heavily contested zones are likely to be relatively peaceful
because denunciations will be deterred by the likelihood
of immediate retribution. 21 and so forth (Erik Gartzke 1999). Such
an account is not inconsistent with formal
theory. Models are seldom intended to be
deterministic but rather to describe general
tendencies. Civil war outbreak is a relatively
rare event and thus it is conceivable that
the basic formal logic is right but at least
some civil wars are in fact costly mistakes.
Indeed, the historical literature is replete
with leaders’ passions, fallibility, and ideology; historians often attribute war and
peace to the attributes of individuals like
Hitler or Gandhi. Some possibilities for
incorporating these issues into formal models already exist. For instance, uncertainty
over whether an opposition leader is an
“irrational” type would affect strategies in
models of asymmetric information.
Third, wars could have determinants that
are outside the simple rational framework,
but systematically so. Some obvious explanations are still consistent with rational models,
such as a leader’s failure to internalize the
full social costs of war—a possibility raised
by Fearon (2004) and recently modeled by
Matthew O. Jackson and Massimo Morelli
(2007) in the context of inter-state war. They
show it only takes one “biased” leader (in the
sense that their returns to war differ from
their citizens’) for war to break out between
A related possibility is that leaders are vulnerable to systematic errors in decision-making, such as overestimating their chance of
winning (overconfidence), time-inconsistent
preferences, or other types of predictable
“irrational” behavior. In such cases, formal
models of conflict may be fertile ground for
application of advances in theoretical behavioral economics. Efforts to incorporate psychological factors and misperception into
international relations theory include Robert
Jervis (1976) and Jack S. Levy (1997), but,
to the best of our knowledge, these insights
have yet to be applied to formal models of
civil war. 22 Journal of Economic Literature, Vol. XLVIII (March 2010) New empirical evidence suggests that
political leaders often do matter. Benjamin
F. Jones and Benjamin A. Olken (2009)
compare successful to failed assassination
attempts, and find that the unexpected assassination of leaders tends to enflame lowscale conflicts and diminish high-intensity
conflicts. Similarly, the unexpected death of
rebel leader Jonas Savimbi is widely viewed
as the event that directly ended Angola’s war,
so much so that Massimo Guidolin and La
Ferrara (2007) use his death in an event study
of war’s termination on diamond company
stock returns. While we think that economic
theory should probably refrain from pinning
too much on personalities, the econometric
evidence just cited means that leadership
cannot be entirely ignored.
This example on the role of leaders suggests that certain determinants of conflict
outside standard models are observable and
testable, and thus could be a basis for new
theory. Furthermore, an important possibility seldom discussed in the recent formal
theoretical literature is that complex, unsystematic, and difficult to observe forces may
greatly influence the outbreak of war, and
make a single general economic theory of
civil war impossible to craft. The need for
intellectual humility is taken for granted by
many civil war scholars (e.g., Cramer 2007).
Even if observable structural factors remain
important, the existence of other influences
will complicate empirical testing, especially
in the statistical analysis of relatively rare
events. We now turn to the evidence, where
the implications of these and other estimation challenges are discussed.
3. Evidence on the Causes of Conflict
The correlates of war are by now wellestablished. Civil war is more likely to occur
in countries that are poor, are subject to negative income shocks, have weak state institutions, have sparsely populated peripheral regions, and possess mountainous terrain.
Ultimately, empirical work should aim to
distinguish which of the competing theoretical mechanisms best explain the incidence,
conduct, and nature of civil war, but this goal
is still far from being realized.26 We have
limited evidence on the relative influence
of the commitment problems and information asymmetries so central to formal theory.
In many cases it is still not clear which of
the above correlates actually cause war and
which are merely symptoms of deeper problems, and we have yet to solve the puzzles
of participation, collective action, and group
cohesion laid out above.
3.1 Cross-Country Evidence
Cross-country regressions dominate the
conflict literature, and no discussion of civil
war empirics is complete without reference
to the seminal contributions of Collier and
Hoeffler (1998; 2004) and Fearon and Laitin
(2003). Collier and Hoeffler ignited interest
among economists—and heated disagreement among scholars in other fields—with
a simple argument: political grievances
are universal but the economic incentives
to rebel are not, and these latter factors
are often decisive. Scores of papers have
ollowed in their footsteps, most sharing a
handful of traits: a dependent variable that
indicates war onset or incidence, proxy variables representing possible causes of conflict,
and a regression-based test of these competing determinants.
Collier and Hoeffler broadly root their
empirical model in a contest model of conflict, and find several variables with robust,
positive correlations with conflict incidence.
First, slow current economic growth is 26 Other recent reviews of the empirical literature,
often spanning economics and political science, include
Collier and Hoeffler (2007), Macartan Humphreys
(2003), Patricia Justino (2007), Kalyvas (2007), Nicholas
Sambanis (2002), and Wood (2003a). Blattman and Miguel: Civil War
ssociated with conflict, as is the proportion
of natural resources in total exports. Higher
levels of secondary school attainment in the
population, in contrast, are associated with a
lower risk of civil war. Meanwhile, a country’s
ethnic fractionalization, income inequality,
and democracy are not statistically significant predictors of conflict risk conditional
on these other factors. Collier and Hoeffler
conclude that economic forces, primarily the
ability to organize and finance a rebellion
(as captured in their economic growth and
schooling variables, and the bility to exploit
natural resources) most strongly predict
whether civil war occurs.
Fearon and Laitin (2003) take a closely
related cross-country approach. Their core
regression, while not derived explicitly from
theory, became the standard formulation for
most cross-country work that followed. It
resembles the logit specification in equation
2, where the dependent variable, ONSETit, is
an indicator for the onset of civil war in country i in year t; CWit is an indicator for the
incidence of civil war (which equals one in
onset and all active war years); yi,t−1 is lagged
per capita income; and Xit is a vector of K
population, geographic, political controls
(including democracy measures) and social
variables (including ethnic and religious
(2) ONSETit = Λ(β 0 + β1 CWi,t−1
+ β 2 yi,t−1 + Xit β K + εit).
′ Like Collier and Hoeffler, Fearon and
Laitin find, first, that conditions favoring insurgency, like rough terrain, increase
the likelihood of civil war, and second, that
proxies for political “grievances” (e.g., ethnic and cultural diversity) have little predictive power. Yet Fearon and Laitin also argue
that proxies for state institutional capacity
and strength—most importantly, per capita
income—are robust predictors of civil war. 23 They conclude that war is engendered by
weak central governments and environmental conditions favoring insurgents.
How do these two papers reach different
conclusions with similar data and econometric techniques? Most importantly, the two
studies attach different interpretations to
key variables like per capita income. Collier
and Hoeffler link it to the opportunity costs
facing potential rebels, while Fearon and
Laitin emphasize its correlation with state
capacity. Yet neither of these two “pure”
nterpretations is entirely justified given the
evidence at hand. The link between income
levels and armed conflict is theoretically
complex, and finer-grained data—say, on
incomes that revert to the state versus the
citizenry, or actual longitudinal measures
of state capacity—is required to distinguish
between these interpretations.
Second, the authors differ in how they
code civil wars. Sambanis (2004) examines
the four competing datasets and finds five
main differences: (i) in thresholds of violence
required to be defined as a civil war; (ii) the
definitions of war beginnings and endings;
(iii) in their treatment of ‘internationalized’
civil war (where there is some involvement
by outside parties); (iv) in their treatment of
related forms of conflict (e.g. communal violence or state repression); and (v) the underlying data sources they draw from.27 Both
Collier and Hoeffler and Fearon and Laitin
examine conflict onset, albeit with different
definitions of war. Other options, however,
27 The coding of civil wars and conflicts remains problematic. Increases in conflict intensity are generally not
captured, except by the 25 and 1,000 death thresholds
in the PRIO/Uppsala data. Some civil “conflicts” may
include low level violence that by other criteria would not
be considered a war (e.g., crackdowns by federal police
on drug gangs). Cramer (2007) reviews other challenges,
including: a large-country reporting bias (where it is easier
to meet the battle death threshold); the emphasis on battle
deaths (omitting, for instance, civilian killings, refugee
movements, and state repression); and difficulties of differentiating conflict lulls from true termination of conflict. 24 Journal of Economic Literature, Vol. XLVIII (March 2010) include conflict incidence (including all years
of war in the analysis) or conflict duration.
These three approaches can be applied to
at least four different civil war datasets, to
create twelve possible dependent variables.
These datasets do not always agree on the
coding of war and correlation coefficients
across datasets range from 0.96 down to 0.42
(with an average of 0.68).28
A third source of inconsistent results lies
in the somewhat ad hoc empirical models
typically used. In this way the cross-country
conflict literature mirrors the earlier debate
assessing the causes of economic growth,
where there was also little agreement on the
correct econometric specification (e.g., Ross
Levine and David Renelt 1992). Authors vary
in their use of annual versus five-year periods, corrections for time dependence, the
treatment of ongoing war years, the appropriate estimator for rare events, the use of
country fixed effects, and so forth.29
Fourth, estimates are sensitive to the
explanatory variables employed. Hegre and
Sambanis (2006) test the sensitivity of estimates to changes in the conditioning set,
using the approach popularized in Xavier
Sala-i-Martin (1997), and identify a few
robust correlates of civil war onset: low per
capita income, slow income growth, rough 28 See Sambanis (2004). These correlations of conflict
onset are likely to exaggerate differences in conflict incidence (since datasets may disagree on the exact year of
conflict initiation). This difficulty and inconsistency in
pinpointing onset will frustrate attempts to relate conflict
onset to time-varying explanatory variables more than
time-invariant ones. The four most common datasets that
Sambanis explores are: the Correlates of War (COW) (J.
David Singer and Melvin Small 1994), Fearon and Laitin’s
(2003) dataset, PRIO/Uppsala (Gleditsch et al. 2002), and
Sambanis’s dataset (2004).
29 On time-dependence and dynamics, see Nathaniel
Beck and Jonathan N. Katz (2004) and Beck, Katz, and
Richard Tucker (1998). On logistic regression with rare
events data, see Gary King and Langche Zeng (2001).
For other issues, see the discussion in Håvard Hegre and
Sambanis (2006). terrain, large population size,30 recent political instability, small government militaries,
and war-prone neighbors. Yet many of these
variables are plausibly endogenous, biasing
other estimates in unknown directions.
Finally, the country level of analysis has
inherent limitations. Individual- and grouplevel conflict factors, such as poverty or
ethnic hostility, are imperfectly tested at
the national level (Sambanis 2004). In such
cases, cross-country evidence (or the absence
of evidence) should be regarded with caution. As we discuss in the next section, microlevel data is likely to yield more convincing
answers to the fundamental theoretical
questions. In our view, other analytical tools,
from case studies to historical analysis, also
3.1.1 Recent Cross-Country Empirical
Recent cross-country research focuses
on improving causal identification and
The search for exogeneity. The correlations of civil conflict with both low income
levels and negative income shocks are arguably the most robust empirical patterns in
the literature cited above, but the direction
of causality remains contested. Even the
use of lagged national income growth (as in
earlier studies) does not eliminate this concern, since the anticipation of future political instability and conflict can affect current 30 The finding on population size suggests a possible
link between population pressure—with its resulting
resource scarcity and environmental degradation—and
civil conflict, a theory that dates back to at least Malthus
(for a review see Thomas F. Homer-Dixon 1999; Colin
H. Kahl 2006). This population pressure hypothesis is
related to the hypothesis that poverty increases armed
civil conflict risk, where rapid population growth could be
one driver of lower per capita income. The link between
population and conflict is complex, however, and could
represent several causal factors (as well as systematic measurement error arising from the coding of battle deaths).
See Gleditsch (1998). Blattman and Miguel: Civil War
investment behavior and thus living standards.31 Another way of saying this is that
there are likely to be permanent fixed differences between countries that are correlated
with their income levels, economic growth
rates, and civil war.
To address this concern, several papers
seek to isolate exogenous variation in income.
In sub-Saharan Africa, where most households rely on rain-fed agriculture, falling
rainfall and drought cause large reductions
in income. Miguel, Shanker Satyanath and
Sergenti (2004) use annual rainfall growth as
an instrument for income growth. The econd
stage estimation equation is as follows, where
CWit is civil conflict prevalence (or onset in
some specifications) in country i in year t,
git denotes per capita income growth, Xit is
a vector of population, geographic, political
controls and social variables, αi is a country
fixed effect (capturing time invariant characteristics that relate to violence, growth, or
both), and δi year t denotes a country-specific
time trend: 25 They use annual country rainfall growth
rates (current and lagged one year) as instrumental variables for the per capita income
growth terms in equation 3. There is a reasonably strong first stage relationship in the
sub-Saharan Africa sample, but it is weaker
in other world regions, where much less
economic activity relies on rain-fed agriculture, making Africa the natural region for the application of this approach. In the
IV specification they find that a 5 percent
drop in income growth increases the likelihood of a civil conflict in the following year
by up to 10 percentage points, or nearly one
half. Antonio Ciccone (2008) reaches the
same conclusion in a modified specification
using log rainfall rather than rainfall growth
as the key explanatory variable. This main
effect is not substantially dampened in countries with stronger democratic institutions,
greater ethno–linguistic fractionalization, or
This analysis highlights the role that
income shocks play in generating armed
conflict in Africa. Unfortunately, this
econometric strategy once again does not
allow the authors to definitively pin down
a unique causal mechanism: rainfall shocks
may provoke conflict because they lower
the pportunity cost of fighting among rural
populations (those most affected by weather
shocks), or because crop failure also reduces
government revenues and state capacity, or
Price shocks provide an alternative means
to study the income–conflict relationship.
Here the evidence is mixed. For instance,
Besley and Persson (2008a) exploit international commodity price movements to investigate civil war causes. Consistent with the
predictions of their theoretical framework
(summarized above), rising import prices lead
to greater conflict, which they argue is due to
a drop in real wages. Export price increases
are also associated with increased civil war
prevalence, since growing government revenue makes seizing the state ncreasingly
i 31 For a discussion of this theoretical point, see
Chassang and Padro-i-Miquel (2007).
32 There may also be other violations of the exclusion
restriction unrelated to economic factors, for instance if
rainfall directly affects the costs of fighting. Moreover, the
authors only study one type of economic shock, mainly affecting the rural sector; variation in national income
induced by changes in industrial production or foreign
aid could conceivably have different impacts. Future work
should also examine the possibility that droughts lead to
violence between settled and nomadic groups, a salient
issue missed in the existing civil war data. (3) ′
CWit = αi + Xit β + γ 0 git
+ γ 1 gi,t−1 + δi yeart + εit . 26 Journal of Economic Literature, Vol. XLVIII (March 2010) attractive.33 However, Samuel Bazzi and
Blattman (2010) reexamine the effect of trade
shocks on civil war using an expanded and
more disaggregated database of international
commodity prices and ountry trade shares.
They suggest that previous results showing a
relationship between trade shocks and political instability (e.g., Brückner and Ciccone
2007; Angus S. Deaton and Ronald I. Miller
1995; Besley and Persson 2008a, forthcoming) are sensitive to the definition of conflict
and to specification. Unlike rainfall, these
shocks show a less consistent relation to conflict, whether they are experienced mainly
by farmers (i.e., agricultural commodities),
the government (minerals and energy), or in
the aggregate. Nor do trade shocks robustly
predict political instability in Africa when
interacted with governance quality, ethnic
fractionalization, or other common explanatory variables, casting doubt on the oft-cited
relationship between trade volatility and civil
conflict, and with it the causal effect of low
incomes on conflict. This question—why
massive trade and income shocks do not seem
to systematically destabilize regimes—is an
important topic of further research, demanding better data, theoretical specification, and
More important than generating any single
result, however, these papers illustrate the
33 Markus Brückner and Ciccone (2007) use terms of
trade shocks (driven by commodity price movements) as
an instrument for national income. They find a large effect
of adverse income shocks on conflict risk among undemocratic African countries. This finding differs from Miguel,
Satyanath, and Sergenti (2004), who do not find any statistically significant interactions between income shocks
and political institutions. Commodity price shocks, while
exogenous, are again plausibly not a valid instrument for
income; these shocks could affect conflict via government
instability (due to collapsing revenues) or by heightening inequality. In this case, a reduced form approach is
less vulnerable to bias than the instrumental variable one
(Bazzi and Blattman 2010). Political instability in even
moderate-sized commodity producers could affect the
world price, making commodity price shocks less exogenous than rainfall. advantage of quasi-experimental econometric approaches for distinguishing correlation
from causation. Indeed, future cross-country
empirical work should achieve more credible
causal inference by focusing on a single, or
small number of, exogenous conflict determinants and plausible instruments for them
rather than running horse races between
many endogenous variables.
More detailed and theoretically motivated measurement. Recent developments
in the literature on natural resources and
conflict illustrate the value of better measurement.34 David K. Leonard and Straus
(2003) emphasize the importance of enclave
production, which has little connection to the
productivity of most citizens (and therefore
may be less vulnerable to civil war violence).
More accurate data have been compiled on
oil production and reserves (Humphreys
2005), while others have done the same for
primary and secondary diamond deposits
(Elisabeth Gilmore et al. 2005), and mineral
rents (Kirk Hamilton and Michael Clemens
1999). Ross (2006) finds that these new and
improved measures of underlying hydrocarbon and diamond deposits are strongly associated with more civil conflict while older
natural resource measures (based on actual
production or exports) show less robust correlations. These findings are consistent with
the contest model’s prediction that insurgencies flourish in resource rich regions because
of the existence of more rents to fight over
and the availability of easy finance, which are
also echoed by some case studies (Philippe
Le Billon 2001, 2005; Ross 2004a).
There remains a need for better measures
of political grievances, institutional quality
and even poverty. Consider political grievances first. Much has been made of the weak
cross-country association between armed
conflict and grievance proxies, including
34 For a review of the literature, see Michael L. Ross
(2004b, 2006) and Humphreys (2005). Blattman and Miguel: Civil War
economic inequality and ethnic fractionalization (e.g., Hegre and Sambanis 2006;
Laitin 2007). This weak association is surprising given the robust negative relationship
between economic performance and some
social divisions, as well as popular perceptions of their centrality in driving conflict
(Alesina and La Ferrara 2005; Alesina and
Roberto Perotti 1996; Easterly and Levine
1997). However, if risk factors like inequality
and ethnic fragmentation are measured with
considerable error, or if their relationship to
conflict is conditional on particular institutional or historical contexts, then we should
not be surprised that their statistical association with conflict is weak. A similar case
could be made about the existing and generally crude measures of state capacity.
A more fundamental concern is that
the existing proxies are theoretically inappropriate. National income per capita, for
instance, may not capture the relevant
aspects of poverty that drive fighting, such
as the roportion of rural male youth living
close to subsistence income. Most measures
of ethnic and religious divisions are used
principally because they are straightforward
to calculate, rather than because they are
theoretically convincing. Indices of ethnic
fractionalization have been questioned as a
meaningful proxy for ethnic tensions (e.g.,
Daniel N. Posner 2004a, 2004b). Here we
have again seen some progress in measurement. Esteban and Ray (1994, 1999) propose
that a bimodal distribution of preferences
or resources—“polarization”—is linked
to greater conflict risk. Jose G. Montalvo
and Marta Reynal-Querol (2005) create
an empirical measure of polarization and
find support for Esteban and Ray’s theory:
while fractionalization is not correlated with
civil conflict, polarization predicts civil war
ncidence. More recently, measures of ethnic
dominance—effectively indicators of minority ethnic rule—have been explored; LarsErik Cederman and Luc Girardin (2007) 27 find that minority thnic rule is associated
with increased risk of war, although once
again this result may not be robust (Fearon,
Kimuli Kasara, and Laitin 2007).
Another area of measurement concern is
income inequality. Some case studies suggest that ‘horizontal’ inequality—inequality
that coincides with ethnic or other politically
salient cleavages—is a particularly important driver of civil conflict (Sambanis 2005;
Frances Stewart 2001). Yet more work is
necessary to code these inequalities, as the
existing data remains fragmented and its sensitivity unexplored (Marie L. Besancon 2005;
Gurr and Will H. Moore 1997; Gudrun Østby
2005). Even with better measures, it remains
difficult to say whether it is the extent of
inequality or its context (factors such as state
strength or the ideological climate) that matter most (Cramer 2003, 2007).
The finding that many civil conflicts
are fought partially along ethnic lines
alone is insufficient to make the case that
thnic-based grievances are driving the fighting. An alternative explanation, for example,
is that the costs of organizing a rebellion
(and collective action more generally) are
simply lower within ethnically homogeneous
groups. Heightened ethnic tension during a
civil war might then be a result of the fighting rather than its cause.
Both the cross-country and case evidence
highlight the susceptibility of states with
weak institutions to civil war. In particular,
partly democratic societies (called anocracies in political science) have emerged as
prime incubators of civil conflict. By this
argument, violent collective action occurs
because dissidents are free enough to organize but nonviolent political activism is typically ineffective (Fearon and Laitin 2003;
Hegre et al. 2001).
Yet recent work suggests such findings
must be taken with caution. For instance,
democracy and anocracy measures, commonly based upon the Polity IV dataset 28 Journal of Economic Literature, Vol. XLVIII (March 2010) (Monty G. Marshall and Keith Jaggers 2006),
explicitly use civil war and political violence
in the coding of the data, thus mechanically
correlating democracy and conflict by definition (James Raymond Vreeland 2008). These
findings highlight the need for better measures of state institutions and less reliance on
existing data. The importance of goverence
persists, however, even after accounting for
the endogenous coding of the Polity IV data.
Goldstone et al. (2010) use conflict forecasting to show that regime type is among the
most robust predictors of civil war onset:
regimes with restricted competition and
some repression of political participation
(anocracies) exhibit the highest relative risk
of war, especially those regimes classified as
partly democratic but factional (in that there
are polarized competing blocs). Their results
find robust support in the case literature (e.g.,
Sawyer 2004, 2005). While predictive rather
than explanatory, such exercises emphasize
the importance of investigating the institutions–conflict link further.
Reviewing the case literature, Sambanis
(2005) suggests several possibilities awaiting empirical exploration: considering new
versus established democracies separately;
the mass popular inclusiveness of political
institutions; the geographic concentration of
power; and the degree of state control over a
country’s geographic periphery. Leonard and
Straus (2003) also emphasize the importance
of direct taxation and institutions of personal
rule.35 Several of these institutional characteristics have yet to be carefully defined and
measured; where they exist, moreover, they
have not been tested against the alternatives.
Finally, while a degree of measurement
error in both dependent and independent variables is an unavoidable hazard of
35 In the former case, Leonard and Straus attempt to
develop a measure of state strength for Africa using direct
taxes relative to national income in the early independence
period. Such worthwhile efforts should be extended. c
ross-country work, few of the papers we
reviewed weigh its consequences on their
estimates. The implications of measurement error ought to be discussed with the
same attention as endogeneity concerns.
Fortunately, instrumental variables estimation addresses attenuation bias due to classical measurement error, and this is one
promising way forward.
Integration with case studies. Historicalpolitical analysis is the most time-honored
approach to the study of civil conflict. New
efforts to integrate case analysis with crosscountry statistical work look to build on the
strengths and minimize the weaknesses of
The clearest example comes from the study
of peacekeeping interventions. Ironically, the
study of peace has given us some of the best
evidence we have for the rationalist roots
of war. Michael W. Doyle and Sambanis
(2000, 2006) review the evidence on United
Nations peacekeeping missions and find that
they are associated with a higher ikelihood
of peace two years after the end of the war.
Virginia Page Fortna (2004a, 2008) examines the duration of peace with and without peacekeepers and reaches a similar
conclusion. Both recognize the limitations
of econometric analysis when missions are
selective and heterogeneous. Fortna shows,
however, how nearly all observable determinants of peacekeeping interventions point to
the U.N. selecting the hardest, rather than
easiest, cases and thus if anything her analysis may be underestimating peace-building
More revealing, however, is the insight
their cases bring to theories of conflict.
Doyle and Sambanis, and Fortna, conclude
that interventions are effective because
peacekeepers (i) change the economic incentives of the armed groups away from warfare;
(ii) monitor and enforce compliance with the
peace agreement; and (iii) facilitate communication between sides, reducing information Blattman and Miguel: Civil War
asymmetries. Agreeing to a foreign intervention, furthermore, is a means for both sides
to credibly signal a commitment to peace.
If keeping the peace requires that external
actors resolve information asymmetries and
commitment problems, it seems likely that
their absence contributed to war in the first
place. The evidence is far from conclusive,
but unlike most cross-country regressions,
these case-based studies specifically grapple
with rationalist theories of war.
Multi-country case studies are also generating new hypotheses and illuminating
some of the causal dynamics driving civil
conflict (Cynthia J. Arnson and I. William
Zartman 2005; e.g., Collier and Sambanis
2005a, 2005b; Fearon and Laitin 2005;
Walter and Jack Snyder 1999). Generalizable
or not, a single case can illustrate possible
causal mechanisms, generate new hypotheses for testing, and stimulate innovative
data ollection. While this case literature
is diverse and impossible to summarize in
full, a number of influential patterns and
mechanisms stand out, including: the conflict-provoking effects of commodity price
shocks on fragile economies (a claim with
only mixed cross-country empirical backing); the central role of external financing
to sustain insurgencies (including providing
cross-border territory for camps, markets for
extracted resources, and military aid); the
pervasiveness of earlier state repression; persistent ethnic or elite class dominance; and
the emergence of insurgencies in peripheral
regions where central government control is
36 For instance, Annalisa Zinn (2005) studies the
Nigerian case, where many factors contributed to civil war
risk but there was no full-blown conflict in the 1980s and
1990s. The federal structure of Nigeria may have helped
diffuse ethnic rivalry at the center. This argument echoes
that of Horowitz (1985) who, in his seminal contribution
to the study of ethnic conflict, argues for federalism as
an institutional reform that changes the locus of political conflict from the center to an increasingly large set of
smaller conflicts in different federal states. 29 Beyond borders. Another promising direction is investigating civil conflict
causes beyond the nation-state. One of the
more novel approaches is taken by Andreas
Wimmer and Brian Min (2006), who use
fixed geographic territories as the unit of
analysis (rather than the more recent nationstate) over two centuries. They suggest that
the likelihood of civil and interstate wars
has been highest during the two massive
institutional transformations that shaped
the modern world: the nineteenth century
incorporation of most of Africa and Asia
into European empires, and mid-twentieth
century formation of nation-states in those
regions. Many wars, they argue, have been
fought to determine states’ governing structures, and so are most likely to occur when
these institutional principles are in flux due
to external geopolitical forces.37
More commonly, researchers looking
beyond borders explore spillovers (or “contagion”) from neighboring countries. Hegre and
Sambanis (2006) find that war in a geographically contiguous country is a robust predictor of armed civil conflict. Kristian Skrede
Gleditsch (2007) finds that the presence of
trans-boundary ethnic groups increases conflict risk, while having stronger democracies
in the region and more interregional trade
are both associated with less civil war. Idean
Salehyan and Gleditsch (2006) provide evidence for another potential source of conflict contagion: refugees. Refugee flows can
ease arms smuggling, expand rebel social
networks, and provide a new pool of rebel
recruits. Looking beyond borders may also
change our perspective on the role of ethnic
“grievances.” Diasporas, whether in neighboring countries or farther afield, driven by 37 Note that Alesina, Easterly, and Janina Matuszeski
(2006) find that artificial states created largely during the
nineteenth century wave of European colonization are no
more likely to experience civil or interstate warfare than
other countries. 30 Journal of Economic Literature, Vol. XLVIII (March 2010) ethnic or religious sentiments often play a
major role in rebel finance.
The empirical salience of these and other
international issues in driving domestic civil
conflicts (including the role of foreign aid,
Cold War interventions, and cross-border
raids) highlights an important limitation of
the existing theoretical work on armed conflict causes, namely its almost exclusive focus
on the internal armed groups’ decision of
whether or not to fight. This is an important
direction for future formal theoretical work,
and will likely draw heavily on the existing
international relations literature.
Conflict duration and termination.
Researchers have also studied war duration and termination.38 For instance, Fearon
(2004), proceeds inductively, sorting cases by
length and looking for salient patterns. He
finds that short wars are disproportionately
initiated by coups and popular revolutions, or
arose from the breakup of the former Soviet
Union and anticolonial wars, all of which seek
political control of the central government.
Meanwhile, autonomy-seeking peripheral
region insurgencies and “sons-of-the-soil”
movements (fought by the local majority
against in-migrants) tend to last much longer.
Researchers commonly use a proportional
hazard model to analyze conflict duration,
employing a variety of economic and social
variables to assess the role of greed, grievance and other factors in the length of
civil wars (e.g., Collier, Hoeffler, and Mans
Soderbom 2004). Others have introduced
more sophisticated methods, including
competing risk models (Karl R. de Rouen
and David Sobek 2004). One finding is that
thnically fragmented and polarized countries experience longer conflicts (Sambanis
and Ibrahim A. Elbadawi 2000; ReynalQuerol and Montalvo 2007). David E.
Cunningham (2006) finds that conflicts are
38 Roy Licklider (1993) provides an influential early
collection of case studies. longer where multiple groups (“veto players”)
must approve a settlement because there
are fewer mutually acceptable agreements,
information asymmetries are more acute,
and shifting alliances create incentives to
hold out, complicating negotiations.
These duration analyses have been useful but suffer from many of the same challenges as the onset and incidence literature:
divergent results using different datasets;
endogenous explanatory variables; and heroic
interpretations of proxy variables. Nonlinear
hazard models also come with additional
identification assumptions, and thus are sensitive to measurement error, repeated and contemporaneous conflict events, and the unit of
time used (Gates and Håvard Strand 2004).
A typology of conflict. Researchers have
analyzed civil war as a single phenomenon by
assumption, leading some political scientists
to ask whether the heterogeneity in types of
civil war should be explicitly incorporated into
empirical models. Are the 1967 Biafran separatist conflict in Nigeria, Nepal’s Maoist insurgency, and the long-running insurgency in
Colombia all examples of the same phenomenon, or should we study them separately?
In response, several papers have begun
to explore new civil war “typologies.” Some
have segregated wars by scale, distinguishing between “conflicts” of 25 to 1,000 battle
deaths per year, versus “wars” of more than
1,000 battle deaths (Gleditsch, et al. 2002).
Others, like Sambanis (2001), explore whether
“identity” (i.e., ethnic and religious) wars have
different causes than ”nonidentity” wars.
Kalyvas (2005, 2007) and Laia Balcells and
Kalyvas (2007) suggest an alternative typology
based on war origins and conduct, identifying
four main classes: “conventional wars” (featuring regular armies and defined front lines);
“symmetric nonconventional wars” with regular armies fighting peripheral or rural insurgencies; “symmetric irregular wars,” fought
between weak national armies and insurgents; and the least common, “urban wars.” Blattman and Miguel: Civil War 31 3.1.2 Further Challenges and Paths Ahead
for Cross-Country Empirical Work Such subclassifications are difficult to test
statistically, as they may only increase the
volatility and sensitivity of empirical results
(especially because it subdivides an already
uncommon event into smaller subcategories
where there may not be statistical power to
demonstrate the validity of a typology). To
the extent that rare events limit the statistical power of such analysis, typology research
will need to lead with theory or case studies
rather than regression analysis.
A further concern is that a generally
accepted approach (and theoretical justification) for subclassification will prove elusive;
the type of civil conflict that occurs—for
instance, a center-seeking versus autonomyseeking civil conflict—is endogenous to state
repressive capacity, rebel organizational
competence, underlying political grievances,
and the likelihood of military success using
that strategy relative to others.
Cramer (2007) challenges civil war
scholars further, asking why civil wars are
nalyzed as phenomena distinct from other
forms of political violence—communal riots,
state massacres, and coups d’état. Neither
the theoretical nor empirical case has been
settled for how to most usefully classify
political violence into different categories.
Moreover, the lines between wars, conflicts,
coups and communal violence are sometimes
ambiguous, potentially leading to errors of
measurement. Exploring these categorical
assumptions is an interesting area for future
analysis, one that could soon be more convincingly tackled with new data on nonstate armed conflicts and “one-sided” state
violence (Kristine Eck and Lisa Hultman
2007; Human Security Report Project 2008;
UCDP 2008).39 Despite the empirical difficulties, we do
not believe that the cross-country regression should be abandoned entirely. But the
path forward looks different than the one
already traveled. Existing empirical models
are too rarely rooted in formal economic theories of conflict, regression functional forms
are too often ad hoc, the selection of proxies is driven by the variables easily at hand
(or online), and their inclusion justified by
informal arguments. As noted above, there is
good reason to believe that the relationships
between civil conflict and income shocks,
ethnic diversity and political grievances
should be conditional ones, evident primarily
when interacted with other contextual variables, and the theorizing and testing of these
potential interactions is a logical next step for
As this literature continues to advance,
there are a handful of best practices to maintain. First, relentless robustness and specification checking. Second, a focus on causal
identification via the use of a single or small
number of exogenous instrumental variables.
Third, the generation of new data on conflict
risk factors and triggers, including better
measures of political grievance and poverty among key population subgroups, and
various dimensions of state institutions and
capacity. Fourth, where measurement error
persists, explicit attention to its ramifications.
Although deriving policy implications is
not the main goal of this survey, there are
some implications of this literature worth
speculating about. The empirical relationship between violence and low and falling 39 The Uppsala Conflict Data Program (UCDP)
defines non-state armed conflict as the use of armed
force between two organized groups, neither of
which is the government of a state, which results in
at least twenty-five battle-related deaths in a year. They define one-sided violence as the use of armed
force by the government or by a formally organized
group against civilians which results in at least twentyfive deaths in a year, excluding extrajudicial killings
(UCDP 2008). 32 Journal of Economic Literature, Vol. XLVIII (March 2010)
3.2 Micro-Level Empirical Evidence on the
Causes of Civil War incomes found in the cross-country literature
suggests that implementing insurance
schemes to protect poor societies from
negative income shocks could be fruitful in
reducing the risk of civil conflict. A number
of authors have recently proposed reforms
to the design of foreign aid and to national
agricultural policies to help blunt aggregate
income shocks and thus help avoid future
rounds of bloodshed (Collier and Hoeffler
2002). One possibility is expanded regional
drought insurance for farmers. A variant is
foreign aid contingent on objective conflict
risk indicators (e.g., weather)—what Miguel
(2007) calls “rapid conflict prevention support”—to bolster local economic conditions
when the risk of political violence is high.40
This example illustrates the potential value
research could have in informing policies to
prevent civil war. Yet while we observe a
poverty–conflict link in the data, too little
is known about the precise identity of the
actual perpetrators and organizers of violence, so the question of which poor to target with assistance to head off violence has
yet to be decisively answered. It also remains
an open question whether interventions that
change incentives for government and rebel
leaders would be more cost-effective than
efforts to target the pocketbooks of potential
rebel recruits. A clearer understanding of
rebel recruitment and organization is necessary for such assessments. These issues (and
others) are beginning to be addressed in the
emerging applied microeconomic research
on civil war. Individuals are the natural unit of analysis for understanding how armed groups
mobilize civilians to fight and contribute
resources to their cause. The black box
assumptions made in theoretical models
on group cohesion and origins need better
justification. In response, the issue of collective action is the subject of a growing
The largest body of evidence comes from
case studies of twentieth century rebellions. Several offer evidence consistent with
models of self-interested actors seeking to
maximize material payoffs. For example,
Mark Irving Lichbach (1994; 1995) illustrates how successful social movements
offer selective material incentives to joiners.
Samuel L. Popkin (1979; 1988) finds that
political entrepreneurs developed mechanisms to directly reward peasant rebellion
in Vietnam. Weinstein (2007) illustrates 40 Targeting this aid toward the social groups most likely
to participate in armed violence—for example, by funding temporary job creation for unemployed young men, or
crop insurance for farmers, increasing the opportunity cost
of fighting in lean years—and in bolstering state capacity
might be most effective in preventing armed civil conflicts
from occurring in war prone countries, most importantly
in sub-Saharan Africa. Several African countries, most
notably Botswana, have already successfully implemented
similar national drought nsurance programs including
public works employment, and these could serve as models (Theodore R. Valentine 1993); Mick Moore and Vishal
Jadhav (2006) discuss a related large-scale rural public
works employment program successfully implemented
in Maharashtra, India. Burke et al. (2009) argue that climate change may increase civil war risk in Africa by over
50 percent to 2030 and that this would make the need for
insurance against weather shocks even more pressing. See
Cullen S. Hendrix and Sarah M. Glaser (2007), Michael
Kevane and Leslie Gray (2008), and David B. Lobell et al.
(2008) for a range of perspectives on the issue of weather,
climate change and conflict in sub-Saharan Africa. The analysis of household and regional data
is a growing, and perhaps the most promising, new direction of empirical research.
Three questions have been of greatest interest so far: (i) the roots of individual participation in armed groups; (ii) the role of internal
geography in influencing where and when
civil conflicts are fought; and (iii) the organization and conduct of conflict.
3.2.1 The Decision to Rebel Blattman and Miguel: Civil War
how in Mozambique, Sierra Leone, and
Peru rebel fighters were remunerated via
looting of civilian property and drug sales.
Material incentives may also be non-pecuniary. Where violence against civilians is
commonplace, joining an armed group
has in many cases been a path to relative
safety (Jeffrey Goodwin 2006; Kalyvas and
Matthew Kocher 2007; Lichbach 1995; T.
David Mason and Dale A. Krane 1989). The
prestige associated with martial success
may also be valued in and of itself.
Yet echoing our discussion above, material
incentives are not always a factor in the individual decision to fight, leading some scholars
to instead argue that moral, ideological, or
ethnic grievances mainly facilitate collective
action. Scott (1976) and Wood (2003b) argue
that moral outrage led people to rebel against
deprivation during economic modernization in Southeast Asia, and over government
abuses in El Salvador, respectively. In neither
case were selective aterial ncentives apparm
ent.41 Another literature documents how
ethnic and social identities have been used
to identify, reward, and sanction free-riders,
thereby providing selective social incentives
to participate (Moore 1993; Elinor Ostrom
1990; Petersen 2001; Weinstein 2007).
A small but growing number of recent
papers employ within-country regional data
to explore the factors that predict violence and
rebellion, and most find strong associations
with local economic conditions. In Indonesia,
Patrick Barron, Kai Kaiser and Menno
Pradhan (2004) find positive correlations
between village-level communal violence 41 Some recent work on terrorism reaches similar conclusions. Alan B. Krueger and Jitka Maleckova (2003)
claim terrorists’ primary motive is passionate support for
their cause and feelings of indignity or frustration, and
that poverty and education play a secondary role. Bueno
de Mesquita’s (2005) formal model allows terrorist organization leaders to sort recruits by quality, possibly leading to the positive selection of terrorists documented by
Krueger and Maleckova. 33 and local unemployment, economic inequality and natural disasters. Using data gathered
from newspaper reports, Daniel L. Chen
(2007) finds that areas of high baseline religiosity experienced more social violence in the
aftermath of the Indonesian financial crisis. In
Nepal, S. Mansoob Murshed and Gates (2005)
find a strong correlation between district-level
civil war deaths and low living standards.
Using the same conflict outcome measure in
seventy-five Nepalese districts, Quy-Toan Do
and Lakshmi Iyer (2007) find that conflict
intensity is strongly and positively related to
the presence of mountainous and forested
terrain, as well as higher local poverty and
lower literacy rates, but is only weakly related
to caste diversity. Karen Macours (2008) uses
different data to argue for another dimension
to Nepalese recruitment: Maoist insurgents
appear to have targeted the districts with the
astest recent growth in income inequality for
These studies are informative and pioneering but many suffer from challenges of
data quality and endogeneity (limitations
the authors are sometimes the first to note).
Further data selection bias worries are introduced when conflict data are assembled from
Western, English-language news reports.
Moreover, individual motivations and decisions are difficult to infer from district-level
aggregate data; just as in the cross-country
literature, there is too often a tendency to
make deep behavioral claims from simple
cross-sectional correlations. The location
of fighting might also reflect armed groups’
strategic considerations (i.e., the location
of important government military targets)
42 One of the drawbacks to reviewing a burgeoning
literature is that it is sometimes difficult for the outsider
(and reviewer) to readily reconcile contrasting results
from different dataset and papers on the same country.
The variety of recruitment and violence patterns found in
Nepal alone is testament to this fact, and we look forward
to more cross-dataset comparisons and weighing of alternative hypotheses for Nepal, as well as other conflicts. 34 Journal of Economic Literature, Vol. XLVIII (March 2010) rather than the underlying socioeconomic
conditions in those areas. Finally, there
remains the possibility of reverse causality;
for example, in a single cross-section, conflict
could contribute to poverty directly, as well
as be driven by poverty itself. Even panel
data is not immune to these concerns, due to
the economic changes driven by anticipated
future conflict or other omitted variables.
Nevertheless, the subnational approach is a
useful step forward.
A recent study by Oeindrila Dube and
Juan F. Vargas (2008) overcomes some of
these concerns, employing exogenous price
shocks and detailed panel data on civil violence—guerilla and paramilitary attacks,
clashes with government military, and civilian casualties—across over one thousand
Colombian municipalities. Consistent with
their theoretical model (which builds on
Dal Bó and Dal Bó 2004), they find that
an increase in the international price of
Colombia’s leading labor-intensive export
commodity, coffee, significantly reduces
violence in coffee-producing regions, while
an increase in the international price of an
important capital-intensive export good,
petroleum, increases violence in regions with
oil reserves and pipelines. In an important
validation of their theoretical model, they
then use rural household surveys to show
that the positive coffee shock affects labor
market outcomes in the hypothesized way,
boosting rural incomes and thus presumably
raising the opportunity cost of participating
in rebellion. A limitation of the study is its
lack of data on actual individual recruitment
into rebel groups or paramilitaries.
To the extent the patterns observed in
Indonesia, Nepal and especially Colombia
are causal, the most likely interpretation is that higher individual opportunity
costs lower the probability of participation in armed groups. We are hopeful that
increased use of innovative micro datasets
will yield a more complete view of the pov- erty–conflict relationship and clarify the
exact echanisms.43 For instance, it remains
unclear empirically whether it is usually the
poorest who actually fight in rebel groups,
and none of these studies tells us by what
means collective action problems are overcome in forming and running armed groups.
A handful of individual- and householdlevel studies are beginning to answer these
central questions. Working in post-genocide
Rwanda, Philip Verwimp (2003, 2005) built
a panel dataset based on a pre-genocide agricultural survey sample. He finds that both
poor wage workers and land renters were disproportionately represented among genocide
perpetrators, and that they appear to have
been motivated by interest in the property
of landlords (who were disproportionately
victims), suggesting a class-based interpretation.44 In Sierra Leone, Humphreys and
Weinstein (2008) collect post-war data on
combatants and noncombatants from the
same villages, and find that retrospective poverty measures (e.g., mud housing), low education, and rebel promises of material rewards
are robustly correlated with recruitment into
armed groups. However, proxies for political exclusion, such as supporting a national
opposition political party, did not predict
participation. Unexpectedly, they also find
that the empirical determinants of voluntary
and forcible recruitment were similar, suggesting that rebel leaders might be employing selective rewards and punishments strategically. Alternatively, it could point to the
limitations of postwar self-reported data
on the rebel participation decision, since
respondents have strong incentives to lie
about the nature of their recruitment and
43 For example, Justino (2009) surveys the emerging
micro-level evidence and suggests that household poverty
interacts with vulnerability (or risk of exposure) to violence in complex ways.
44 Catherine André and Jean-Philippe Platteau
(1998) find related results. See also Straus (2006) on the
Rwandan Genocide. Blattman and Miguel: Civil War
wartime behaviors ( laiming abduction even
if they in fact volunteered to fight), to escape
social disapproval or even legal prosecution.
Taken together, these studies suggest that
material incentives are influential in driving
killing even in the most brutal civil wars and
in genocide—supposedly the quintessential
act of irrational hatred. Proxies for political
grievances perform far more poorly at predicting individual behavior than economic
factors in these cases. Existing data on political grievances are admittedly quite coarse
and may not adequately account for context
specificity, but this provides evidence against
the view that political grievances are always
decisive determinants of participation in
armed groups. We again return to the need
for detailed micro-data—ideally, individual
panel data collected comparably across countries—on political attitudes and grievances,
incomes and labor market opportunities, as
well as local government budgets and security capacity in order to more conclusively
disentangle competing explanations for participation in civil conflict.
The above examples also call attention to
the importance of measuring the incentives
offered by armed organizations. A robust
assessment of competing explanations for
rebel recruitment would require data on
the individual characteristics of rebel participants and non-participants, as well as
the recruitment “offers” received by both
types of individuals, both offers taken and
those refused. These data will obviously be
extremely challenging to collect, especially
retrospective data given the high and selective mortality experienced during wartime,
and will likely require greater oordination
between researchers, governments and
humanitarian aid donors.
3.2.2 Internal Geography
Like recruitment, geographic patterns of
conflict within states are best explored using
sub-national data. To this end, researchers 35 in organizations like the International Peace
Research Institute of Oslo (PRIO) and the
University of Uppsala have begun to construct and analyze sub-national conflict datasets. Early results are largely consistent with
the existing cross-country and case evidence
on the role of geography. Halvard Buhaug
and Jan Ketil Rød (2006), for instance, disaggregate conflict and geographic country
data into 100 kilometer by 100 kilometer
grids within Africa, and find that separatist
conflicts are more likely to occur in sparsely
populated regions near national borders, at
greater distances from the capital (where
political control by the central government is
likely costlier), and in the vicinity of petroleum
fields, where the rents of political power for
secessionists are presumably highest.45 The
existence of easily lootable resources in the
context of a bitterly poor society also drove
violence in Sierra Leone’s war: there are significantly more armed clashes within chiefdoms containing greater diamond wealth
(John Bellows and Miguel 2009). Joshua D.
Angrist and Adriana D. Kugler (2008) similarly find that an increase in world cocaine
prices led to increased civil conflict violence
in coca growing regions of Colombia relative
to other parts of the country.
3.2.3 The Organization and Conduct of
Another direction is empirical research on
the fighting factions themselves. Theoretical
progress in this area accelerated some years
ago, and we now have a host of theories of
45 A closely related approach examines the geographic
features of civil wars, such as the size of the conflict zone
or the distance from the capital. Buhaug and Gates (2002)
build a database of battle sites and find that wars of secession and wars with an ethnic or religious dimension tend
to fought in the peripheries. Larger conflict zones are
associated with border zones, the presence of natural
resources, and peripheral conflicts. While interesting, it
remains to be seen what such associations can add to a
theoretical understanding of civil war. 36 Journal of Economic Literature, Vol. XLVIII (March 2010) rebel and terrorist organization, several of
which we reviewed above, as well as extensive case evidence.46
Systematic evidence on armed group organization and action, however, has lagged
behind. Economists and political scientists have begun to conduct surveys of excombatants in Burundi, Colombia, Liberia,
Sierra Leone, and Uganda (Jeannie Annan
et al. 2008; Ana M. Arjona and Kalyvas
2008; Humphreys and Weinstein 2004; Eric
Mvukiyehe, Cyrus Samii, and Gwendolyn
Taylor 2008; James Pugel 2007), some still
works in progress. These surveys explore who
the combatants were, where they came from,
and their prewar experiences. Comparisons
across armed groups, or to civilians, suggest
motivations for joining an armed group or
committing particular acts of war.
Such data have limitations, however: they
are self-reported; they are based on a sample of survivors; and they can seldom move
beyond descriptive analysis of who joins
and why. Isolating exogenous variation in
recruitment, tactics, or exposure to violence
is crucial for drawing firm conclusions. For
instance, to understand the determinants of
civilian abuse, Humphreys and Weinstein
(2006) construct military unit-level measures of discipline and civilian abusiveness
that are exogenous to the individual respondent. However, the sample size is such that,
unfortunately, there are seldom more than
one or two observations per unit. Beber and
Blattman (2008) use new data on ombatants,
and exogenous constraints on rebel recruitment, to understand the logic of coercive
child recruitment in northern Uganda.
Unpopular and short of funds, the rebel
Lord’s Resistance Army had just one means
of gaining recruits: abduction, followed by
the constant threat of punishment against
46 For case studies on African guerrilla movements,
see Christopher S. Clapham (1998) and Morten Bøås and
Kevin C. Dunn (2007). new recruits. The likelihood of receiving a
firearm and self-reported dependability was
increasing in age, while loyalty and length
of stay fall in age. From a rebel perspective,
the intermediate age group—young adolescents—were the most attractive recruits,
suggesting that coercion and child soldiering
go hand in hand.
Deliberately indiscriminate violence
against civilians may be another source of
exogenous variation. Kalyvas (2006) documents 100 studies and 45 historical cases
where state violence against noncombatants
provoked greater insurgent violence as a
response. In a recent micro-empirical study,
Jason Lyall (2009a) examines the effect of
Russia’s purposefully random shelling of
Chechen villages on insurgent activity. This
paper, one of the few to arguably study random violence, comes to the opposite conclusion: insurgent attacks in the village and its
neighbors decline after shelling.47 However,
he is reluctant to draw conclusions about how
violence in a particular place translates into
long-term outcomes there, and the generality
of this result is unclear.
Counterinsurgency is a topic of major current interest in the wake of the U.S.-led wars
in Iraq and Afghanistan. Military analysts
and commanders have written extensively
on theories and lessons learned in the field
(e.g., Richard L. Clutterbuck 1966; David
Galula 1964; H. R. McMaster 2008; John A.
Nagl 2002; David H. Petraeus 2006; Kalev
I. Sepp 2005).48 Researchers have begun to
investigate the efficacy of recent U.S. counterinsurgency operations. Berman, Shapiro
and Joseph H. Felter (2008) find that the
47 Lyall (2009b) compares “sweep” operations by
Russian and pro-Russian Chechen forces during the war
in Chechnya (2000–2005). Co-ethnics appear to be better
at counterinsurgent operations: comparing sweeps in pairs
of similar settlements, insurgent attacks increase after
Russian sweeps but decline after Chechen operations.
48 Stephen Biddle et al. (2008) review military counterinsurgency research in political science. Blattman and Miguel: Civil War
disbursement of small-scale reconstruction
funds by U.S. field military commanders in
Iraq is correlated with lower levels of insurgent attacks. Of course, selection on unobserved traits, or regression to the mean,
could be driving this apparent effect; for this
reason, a number of experimental and quasiexperimental evaluations of counter-insurgency spending are presently underway.49
Some recent work finds that armed groups
respond strategically to new information.
Radha Iyengar and Jonathan Monten (2008)
develop data on insurgent attacks and media
coverage in Iraq, and find an “emboldenment” effect of new information about U.S.
withdrawal intentions on the pace of insurgent attacks. They use this evidence to show
that insurgent organizations are sophisticated
strategic actors, but while doing so also illustrate the existence of asymmetric information between the warring parties. This work
advances our understanding of the empirical
relevance of the information asymmetries
that are so prominent in theoretical work.
3.2.4 Next Steps
There are four main limitations to this new
applied micro-empirical literature. First, the
necessary datasets are expensive, hard-won,
and often require a mix of luck and ingenuity.
Hence they are too few in number. Second,
sufficient attention has often not been paid
to measurement issues, research design,
and econometric identification. Too many
researchers have rushed to collect microdata without adequately preparing a research
design in advance, or testing the assumptions required for causal inference. Third, it
remains to be seen whether and how microlevel results will test conflict theories. In
49 Of note is the U.S. Defense Department’s Minerva
Research Initiative, which in cooperation with a consortium of university researchers, is supporting rigorous
impact evaluations of development and military programs to build peace in Iraq, Afghanistan, the Caucasus,
Philippines, and elsewhere (Princeton University 2009). 37 particular, while counter-insurgency studies
have inherent military value, it is not always
clear how they relate to broader theoretical
debates. Fourth, it remains to be seen how
micro-level insights from one war generalize to other contexts, and thus can be useful for policymakers elsewhere. At this early
stage, this is primarily an argument in favor
of increasing the number of micro-empirical
studies on the causes and conduct of civil war.
4. Economic Legacies of Civil Conflict
People living in zones of war are maimed,
killed, and see their property destroyed.
They may be displaced, or prevented from
attending school or earning a living. A growing empirical literature estimates the magnitude of these effects of war on later income,
overty, wealth, health, and education.50
Each of these outcomes has implications
beyond the individual, however. To the extent
that these costs are borne unequally across
groups, conflict could intensify economic
inequality as well as poverty. The destruction
(and deferred accumulation) of both human
and physical capital also hinder macroeconomic performance, combining with any
effects of war on institutions and technology
to impact national income growth.
Understanding the economic legacies of
conflict is also important to the design of
postconflict recovery. If war itself further
aggravates factors that enhance the risk of
civil conflict—poverty, inequality, and social
discord—then it could partially account for
Indeed, the aggregate effects of armed
conflict, and its threat, are considerable.
Dani Rodrik (1999) argues that outbreaks
of social conflict are a primary reason why
50 Justino (2007, 2009) also surveys this emerging
literature. Many of the datasets and working papers are
being shared via research groups such as the Households
in Conflict Network (http://www.hicn.org). 38 Journal of Economic Literature, Vol. XLVIII (March 2010) national economic growth rates lack persistence and why so many countries have
experienced a growth collapse since the mid1970s. A number of cross-country growth
studies link measures of political instability
to large negative effects on national savings,
investment, income and growth.51 Valerie
Cerra and Sweta Chaman Saxena (2008) find
that output declines six percent in the immediate aftermath of a civil war. Quantitative
case evidence supports this cross-country
relationship: Alberto Abadie and Javier
Gardeazabal (2003) find that terrorist violence in the Basque region of Spain has significantly reduced economic growth there
relative to neighboring regions. The effect on
poverty can be dramatic. In Rwanda, 20 percent of the population moved into poverty
following the genocide (Justino and Verwimp
2006). Civil wars may also have negative
growth spillovers on neighboring countries
(James C. Murdoch and Sandler 2004).
An economic growth theory framework
is useful for analyzing the consequences of
conflict. If conflict affects economic performance, it must be because it affects a factor of production (physical capital, labor, or
human capital), the technology, institutions,
and culture that augment these factors, or
prices (e.g., costs of capital). The growth
framework also clarifies the possible nature
of the impacts, not only on income levels
and economic growth in equilibrium, but
also out-of-equilibrium dynamics such as the
speed of convergence.
The framework we use to organize our
discussion is based on neoclassical models of growth with human capital (e.g.,
Robert E. Lucas 1988; N. Gregory Mankiw,
David Romer, and David N. Weil 1992).
51 See Robert J. Barro (1991), Alesina et al. (1996),
Alesina and Perotti (1996), and Svensson (1998). The
political instability-growth relationship may be partly
endogenous but some argue that the association is likely to
persist even after better accounting for this bias (Kwabena
Gyimah-Brempong and Thomas L. Traynor 1999). Alternative frameworks, however, can generate radically different predictions regarding
the likely impact of violence—and, in particular, the destruction of capital—on economic performance. To illustrate, a one-time
shock to capital has no effect on equilibrium
income or growth in a neoclassical model,
but persistent effects are possible in poverty
trap, endogenous growth, and vintage capital models (e.g., Costas Azariadis and Allan
Drazen 1990; Barro and Sala-i-Martin 2003;
Simon Gilchrist and John C. Williams 2004).
The relative degree of physical and human
capital destruction also matters: recovery
could be faster under highly asymmetric
destruction—say, extensive physical capital
destruction when human capital remains
largely intact—since the relative abundance
of one type of capital raises the marginal
product of the scarce type, spurring on
investment. Barro and Sala-i-Martin (2003,
p. 246) describe this “imbalance effect” in a
one-sector endogenous growth model with
physical and human capital, with the following production function:
(4) Y = AK α (Lh)1−α, where A, K , and L have the usual interpretations as technology, physical capital,
and workers, respectively, h denotes average worker human capital, and total human
capital is H = Lh. They examine the case
where the K /H ratio deviates from its steady
state value of α /(1 − α), for instance due to
war damage; capital investments are irreversible; and there are adjustment costs to
apital accumulation. When adjustments
costs for human capital accumulation are
greater than for physical capital investment,
which seems plausible empirically, the disproportionate loss of human capital in war
results in slower economic growth and
recovery than the destruction of physical
capital, during the transition back to steady
state growth. Blattman and Miguel: Civil War
Given the proliferation of plausible theoretical perspectives, empirical evidence is
essential. Yet assessing the economic consequences of civil war is complicated by a central
identification problem: war-torn countries
are different than peaceful ones (as detailed
in sections 2 and 3). Poor postwar economic
performance could reflect the declining economic conditions that contributed to armed
conflict in the first place, in addition to any
direct impacts of war. Similar endogeneity concerns arise in assessing impacts on
government performance and institutions,
and even individual-level outcomes (to the
extent different types of individuals are targeted for violence or recruitment into armed
groups). The existing empirical literature on
postwar economic recovery is only beginning to seriously address these issues, and as
a result the conclusions we can draw about
the onsequences of war, and the appropric
ate postwar policy responses, are more limited than in the case of civil conflict causes
4.1 Physical Capital and Investment
Evidence from interstate wars suggests
that the postwar evolution of physical
capital often behaves as predicted by the
neoclassical model, namely, rapid recovery to equilibrium levels. One set of studies examines the impact of U.S. bombing
on later outcomes at the city or regional
level. Although they generally lack detailed
information on local physical capital levels, in Japan (Donald R. Davis and David
E. Weinstein 2002) and Germany (Steven
Brakman, Harry Garretsen, and Marc
Schramm 2004) in World War II, cities
that were heavily bombed quickly recover
in population back to prewar trends, such
that 20 to 25 years postwar city populations
are indistinguishable from cities that were
left untouched by bombing. In the Vietnam
War, which combined external intervention
and a civil war, Miguel and Gerald Roland 39 (2006) find similarly rapid local population
recovery from bombing.
These cross-region results echo the consensus from the cross-country literature on
the rapid recovery of postwar economies (A.
F. K. Organski and Jacek Kugler 1977, 1980;
Adam Przeworski et al. 2000). Indeed, a
recent study of the output response to alternative crises—including currency crises,
bankingcrises, civil war, and sudden shifts in
executive power—finds that while civil wars
cause the steepest short-run fall in output
(six percent on average), only in the case of
civil war does output rebound quickly, recovering half of the fall within a few years, while
output drops are more persistent for financial
crises (Cerra and Saxena 2008). While such
event studies conceal a great deal of heterogeneity in experiences, and suffer from obvious omitted variable bias concerns, none of
these results appear consistent with poverty
trap models of economic growth such as
those recently advanced by Jeffrey D. Sachs
Nevertheless, there are reasons to be
cautious in generalizing these experiences.
These studies cannot rule out the possibility that the economic devastation caused
by civil war prevent some countries from
achieving durable peace. Countries with successful postwar economic recovery are also
more likely to collect systematic economic
data, introducing possible selection bias:
war-torn countries where the economy and
institutions have collapsed (e.g., Congo and
Somalia) lack good data, while those that
recover (Vietnam) have data. This could
bias the cross-country estimates of war’s
economic impacts towards zero as the most
destructive wars exit the sample. Civil wars
are also often localized and fought with small
arms and munitions, so they do not necessarily see the large-scale destruction of capital
caused by bombing, creating some separation between the evidence we have and the
contexts of greatest interest. 40 Journal of Economic Literature, Vol. XLVIII (March 2010) Yet even in civil conflicts without largescale bombing, capital can sometimes be
depleted in devastating ways. First, household assets may be stolen or destroyed.
Mozambicans, for instance, are thought
to have lost 80 percent of their cattle stock
during their civil war (Tilman Bruck 1996),
while many in northern Uganda lost all
of their cattle, homes and assets (Annan,
Blattman, and Roger Horton 2006; Robert
Gersony 1997); cattle and other farm assets
often represent most of a rural household’s
savings. As of yet, however, there is still limited systematic panel data on the implications of such asset loss on long-run household
welfare. Second, countries at war are likely
to see massive flight of mobile forms of capital, since foreign assets offer higher relative
returns at lower risk (Collier 1999; Collier,
Hoeffler, and Catherine Pattillo 2004). The
same factors could lead to such low levels of
new investment that the existing capital stock
The neoclassical growth model prediction that the capital stock should return
to its steady state level once the fighting
stops—implying relatively high returns
and rates of investment that decline as the
equilibrium is approached—supposes that
underlying institutions and technology are
largely unaffected by the fighting, and that
military spending, the returns to capital
investment and the cost of capital similarly
return to prewar levels. Yet any political or
economic uncertainty following war is likely
to decrease expected returns, increase relative risk, and possibly shorten investment 52 Rising military spending can also crowd out government infrastructure projects and other public goods. A
World Bank report estimates that average military spending in poor countries rises from 2.8 percent of national
income in peace to 5 percent at war (Collier et al. 2003).
Cross-country evidence suggests that such military spending is growth-retarding due to the shift away from productive investment (Norman Loayza, Malcolm Knight, and
Delano Villanueva 1999). horizons, thus reducing investment and raising the cost of capital. Collier (1999) argues
that adverse effects on the cost of capital are
sometimes persistent empirically.
Foreign financial aid and other international interventions could play an important
role in rebuilding infrastructure and replenishing household assets in these cases. There
is also anecdotal evidence from countries
like Sierra Leone and Liberia that the role of
the international community was decisive in
shifting expectations about future conflict risk
(Collier 2007). Collier and Hoeffler (2002)
suggest that increased foreign aid is likely
to reduce civil conflict risk, and find some
modest reductions in the likelihood of conflict for aid recipients, working through the
channel of faster economic growth. Yet the
nonrandom placement of both civil conflicts
and foreign aid means we cannot necessarily interpret these statistical relationships as
causal. Joppe De Ree and Eleonora Nillesen
(2006), however, examine aid disbursements
and civil conflict risk in sub-Saharan Africa
using an instrumental variable strategy that
exploits exogenous changes in donors’ overall
foreign aid budgets, and they find that a 10
percent increase in aid to an African country reduces conflict risk by 6 percent. Taken
together, these two studies suggest that postwar foreign aid may play a key role in solidifying the transition to peace.53
Future advances could come from disaggregating such postwar aid flows and investigating the role of specific activities (such as
peacekeeping) on reducing risk and promoting economic recovery. Recently Collier, Lisa
Chauvet and Hegre (2008) attempt just such
a cost–benefit analysis of alternative aid and
military interventions. Such calculations are 53 An emerging literature examines the role that postwar demilitarization programs (usually funded by aid
donors) could play in securing the peace, although there
is little quantitative evidence on the effectiveness of these
programs. Blattman and Miguel: Civil War
highly dependent on parameters for which we
currently have limited data (e.g., the growth
effects of avoiding a civil war, the selection
of countries into different interventions) and
thus have to be interpreted with caution.
4.2 Life, Labor, and Human Capital
Wars kill and maim people, both directly
and indirectly through famine and disease.
Conflict victims are overwhelmingly civilians, and indirect deaths are seen disproportionately among the poor, women, children
and the elderly.54
The short-run impact of war is clearly disastrous, but there is mixed evidence on how long
the economic effects on human capital and
quality of life persist. In the study of Vietnam
bombing mentioned above, local living standards and human capital levels also converged
rapidly across regions after the war, leaving
few visible economic legacies twenty-five years
later (Miguel and Roland 2006). This empirical finding echoes the cross-country literature
showing rapid post-war economic recovery
and argues against poverty trap type models.
An innovation is the attempt to address the
endogeneity of bombing. Miguel and Roland
instrument for bombing intensity using distance from the arbitrarily settled North-South
Vietnamese border (on the 17 th parallel north
latitude).55 A limitation of this paper—and
others that examine differences across subnational units over time—is its inability to
credibly estimate the aggregate national economic impact of war damage; for that, crosscountry studies may be more convincing.
A new and rapidly growing microeconomic
literature finds more persistent negative war
54 Wars are thought to have directly caused 269,000
deaths and 8.44 million disability-adjusted life-years
(DALYs) in 1999 alone, with twice again this number of
deaths and DALYs estimated in 1999 due to the lingering effects of wars between 1991 and 1997 (Hazem Adam
Ghobarah, Paul Huth, and Bruce Russett 2003, 2004).
55 Districts located near the border were subject to more
fighting, cross-border raids, artillery shelling, and bombing. 41 impacts on individual human capital, especially in African cases. Using panel data
on child nutrition, Harold Alderman, John
Hoddinott and Bill Kinsey (2006) find that
young children who suffered from warrelated malnutrition in Zimbabwe are significantly shorter as adults, which may
affect their lifetime labor productivity. In a
related paper, Tom Bundervoet, Verwimp,
and Richard Akresh (2009) exploit variation in the timing of armed clashes in the
Burundi civil war to estimate impacts on
child nutrition, and find that children who
lived in a war-affected region have sharply
lower height-for-age than other children,
with an average drop of roughly 0.5 tandard
deviations. Turning to a Central Asian setting, adolescent Tajik girls whose homes
were destroyed during that civil war are less
likely to obtain secondary education, again
with likely adverse effects on later wages
and life chances (Olga Shemyakina 2006).
The validity of these studies, all of which use
difference-in-differences methods, relies on
the assumption of similar underlying human
development trends in the war-affected and
peaceful regions of these countries, something that is challenging to convincingly
establish with the limited time horizons of
most datasets.56 Moreover, as in the ombing
studies, these studies may underestimate
war’s overall impacts to the extent that even
those in largely peaceful regions were also
adversely affected by civil war disruptions.
Turning to combatants, it appears that the
interruption of human capital accumulation is
one of the most pervasive impacts of military
service. Studies of U.S. and European veterans of the Vietnam and Second World Wars
find large and persistent falls in earnings
56 An unexpected spillover effect of war on the human
capital of neighboring countries comes from Montalvo and
Reynal-Querol (2007) who, using civil wars as an instrumental variable, argue that for each 1,000 refugees there
are between 2,000 and 2,700 additional cases of malaria
in the refugee-receiving country. 42 Journal of Economic Literature, Vol. XLVIII (March 2010) and higher mortality (Angrist 1990, 1998;
Angrist and Krueger 1994; Norman Hearst,
Thomas B. Newman, and Stephen B. Hulley
1986; Guido Imbens and Wilbert van der
Klaauw 1995). These patterns are echoed by
new evidence from developing countries. For
instance, Blattman and Annan (forthcoming)
and Annan et al. (2009) use exogenous variation in rebel recruitment methods—namely,
near-random forced recruitment in rural
Uganda—to estimate its impact on adolescents and young adults. These conscripts are
more likely to have persistent injuries, accumulate less schooling and work experience,
are less likely to be engaged in skilled work,
and earn lower wages as adults (especially
males). Psychological trauma and community rejection, meanwhile, are concentrated
in the small minority that experienced the
most violence.57 The conclusion that emerges
is that military experience is a poor substitute for civilian education and labor market
experience. In settings where a large share of
youth actively participate in fighting, aggregate economic impacts could be quantitatively important.
This emerging applied microeconomic literature only scratches the surface of the range
of possible civil war impacts on the economy
and society. More evidence is required on
the educational, employment, and health
impacts of conflict on armed group participants and civilians, including internally displaced people. The leading question is not
whether wars harm human capital stocks, but
rather in what ways, how much, for whom,
and how persistently—all crucial questions
for understanding war’s impacts on economic
growth and inequality, as well as priorities for
postconflict assistance. To our knowledge, no
57 A somewhat different pattern is observed by
Humphreys and Weinstein (2006, 2007), who find that
increases in Sierra Leone fighters’ exposure to violence
are correlated with lower postwar community acceptance,
but also find that violence has little correlation with labor
market success. rigorous evidence yet exists on which types
of programs are most effective at overcoming war’s adverse legacies on human capital.58
4.3 War, Institutions, and Society
The steady state to which a postconflict
society returns is a function of the fundamental determinants of growth: technology, institutions, and social organization. The rapid
return to prewar levels of labor and capital in
Germany, Japan, and Vietnam noted above
suggests that these determinants were not
diminished by war (or, if they were, they likewise recuperated quickly).
Unfortunately, we have little systematic
quantitative data with which to rigorously
judge claims about the evolution of institutions during and after civil wars. A sizable
literature has sought to identify the specific institutional factors that matter most
for economic growth—including property
rights (Acemoglu, Simon Johnson, and
Robinson 2001), social capital and cohesion
(Stephen Knack and Philip Keefer 1997),
rational bureaucracies, and work ethics, to
name a few—but which of these are affected
by civil war (not to mention how much and
under what circumstances) remains a matter of speculation. The social and institutional legacies of conflict are arguably the
most important but least understood of all
58 Other potentially important topics awaiting systematic empirical analysis include: the role of war-related
emigration (especially of the skilled) on later economic
growth, the general equilibrium effects of death and
emigration on labor markets, and civil war’s effects on
the prices of land, capital, and labor. Abbey Steele (2007)
includes a review of the determinants of population displacement, while Florence Kondylis (2008a, 2008b) presents quasi-experimental evidence on some of its economic
impacts. To the extent that the sudden death of sizable
shares of the working age adult population affects relative prices, fertility and investment decisions, civil war
could have impacts on living standards reminiscent of the
HIV/AIDS epidemic in sub-Saharan Africa along the lines
argued in Alwyn Young (2005). Blattman and Miguel: Civil War
The historical evidence (described above)
that war enables the development of capable
government institutions in Europe may not
generalize to civil war cases. In the three
countries that experienced U.S. bombing,
the wars were fought against (largely) foreign armies, and hence could rally citizens
and renew government motivation and legitimacy. In civil war, government may lose
legitimacy, while victors and vanquished
(and victims) are condemned to coexist in the
same society, potentially exacerbating political and social divisions.
Yet even the waging of internal war need
not always be uniformly destructive to institutions. The effort to control the nation’s
peripheries, and the extension of national
control down to the community level are
essential state responsibilities. Successful
states do so through a variety of means,
including the use of force (Tilly 1982;
Max Weber 1965). Hence internal warfare
could hypothetically generate state-building rather than institutional disintegration. Yoweri Museveni’s violent takeover
of the Ugandan state, for instance, hinged
in part on his ability to organize citizen
councils from the village up to the national
level—councils that became the basis for
postwar administration and (especially by
regional standards) a relatively strong state
Indeed, there is some cross-country evidence that wars that end in outright military victory for one fighting side lead to a
more stable peace and possibly stronger
state institutions (Fortna 2004b; Monica
Duffy Toft 2008), although once again the
omitted variables correlated with outright
military victories make interpretation of
this pattern difficult. A draw, a negotiated
agreement, or a ceasefire is, by this logic,
an unstable equilibrium bound to unravel.
This belief has led some scholars to argue
that the international community should
“give war a chance” (Herbst 2000; Edward 43 N. Luttwak 1999). In an indication of how
unsettled the literature currently is, another
recent case study and statistical analysis
indicates that aggressive peacekeeping leads
to more lasting peace (Fortna 2008; Human
Security Report Project 2008; Sambanis
2007). Easterly (2008) argues against this
view, however, pointing out that there are
as many examples of failed foreign interventions (e.g., Darfur, Democratic Republic of
Congo, Somalia) as successes (Sierra Leone).
One reason why research has produced few
definitive answers so far may be that there is
no simple, general relationship between civil
war and institutions; impacts may depend
on why a war started in the first place, how
it is fought, and how it ends.59 The unpacking of these complex relationships is perhaps
the most pressing area for future empirical
research in this area. While the war termination literature tends to focus on the durability of peace agreements, a useful next step is
to focus on patterns of institutional change
during and postconflict. While the analysis
of these relationships is clearly full of omitted variable bias concerns, the search for
innovative research designs should continue.
Beber (2008), for instance, uses the higher
likelihood of mediated bargaining occurring
during the summer months (when foreign
politicians and diplomats are freer to broker
deals) to identify the gains to mediation in
A final perspective on the institutional and
social impacts of war comes from an empirical literature on postwar political participation and accountability. Of the preliminary
data available, some of the results are quite
counterintuitive, especially an apparent
causal link between war violence and productive citizenship postwar. A recent microstudy finds that war victimization increases
later individual political mobilization and
59 The literature on war termination in particular is
vast, and is outside the scope of this review. 44 Journal of Economic Literature, Vol. XLVIII (March 2010) participation in local collective action in
Sierra Leone, which the authors interpret
as a result of the psychological legacies of
individual violence exposure (Bellows and
Miguel 2006, 2009). Former combatants
in Uganda were also more likely to vote
and become local leaders (Blattman 2009).
Likewise, psychologists find that the victims
of violence are in general resilient (Ann S.
Masten 2001), and that exposure has even led
to greater political activism among groups
such as Jewish Holocaust survivors (Devora
Carmil and Shlomo Breznitz 1991) and
Palestinian victims of bombardment (RaijaLeena Punamäki, Samir Qouta, and Eyad El
Sarraj 1997). Together, these ndings begin
to challenge the notion that the motivations,
institutions, and social norms that promote
local level collective action are necessarily
harmed by civil war.60
4.4 Remaining Challenges
Viewed through the lens of economic
growth models, the existing empirical literature on civil war impacts still looks spotty.
Macroeconomic studies indicate that the
short-run output effects of armed conflict
can be large, but more work is needed to
examine the underlying effects on factors
of production and relative prices. The early
signs suggest that population and physical
capital can fully recover after war, perhaps
as quickly as within two decades. That
recovery, however, appears to be contingent
on the preservation, or even the improvement, of political stability and institutions,
as was the case in Japan, Germany, and
Vietnam. Yet what the key institutions are,
and which domestic policies and external
60 Yet findings are far from uniform. Miguel, Sebastian
M. Saiegh, and Satyanath (2008) argue that civil wars
may shape national socio-cultural norms toward violence.
They find that European soccer league players from countries with histories of civil war commit significantly more
violent yellow and red card fouls (conditional on player
characteristics). interventions can help maintain their stability, are still poorly understood. Even
theoretically compelling patterns could be
spurious, driven by omitted variables rather
than causal impacts.
The microeconomic literature is even less
systematic at present, although in our view it
holds great promise. Many factors appear to
be adversely affected by civil war in at least
some cases. Those who participate in wars, or
simply live through them, often suffer from
persistent injuries, lose out on education,
and see a permanent decline in their productivity and earnings. But understanding
which impacts are more profound and persistent than others; which disproportionately
strike the poor; and how those effects can be
ontained by local institutions and economic
policies is still largely unexplored.
Without firm answers to these questions,
policymakers and foreign aid donors have
often taken a scattershot approach to postwar programs. The subject of post-conflict
recovery policy is vast and is largely outside
the scope of this review, but most of that literature comes in the form of best practices
summaries, case studies, and other literature produced by international aid organizations, governments, and NGOs. Academic
research remains limited, and where it exists,
tends to focus on high-level analysis (e.g.,
the relationship between aggregate foreign
aid and national economic growth) and so
is largely unhelpful to those seeking specific
programmatic solutions. Given the many
possible omitted variables involved in the
timing of foreign interventions, related to
both domestic and international political factors, establishing the causal impact of armed
intervention on long-run political and economic outcomes has been elusive.
An obvious answer is to call for more data
collection, continued searching for natural
experiments or actual field experiments, and
more rigorous impact evaluations of postconflict programs. Judging by the rise of research Blattman and Miguel: Civil War
organizations like the Households in Conflict
Network (HiCN), increased funding by the
World Bank’s Development Research Group,
and the growing literature, this call for more
and better analysis is already beginning to be
5. Discussion and Future Directions
Armed conflict is finally moving into the
research mainstream in development economics. This article has attempted to survey this flourishing interdisciplinary field,
describe its more robust findings, and point
the way forward in a way that is useful for
both those new to the field as well as those
already actively working within it.
Some of the core insights are worth restating here. First, there has been considerable progress in the formal modeling of the
political economy of civil war during the
past two decades, with insights on the individual decisions, institutional features, and
economic conditions that promote violent
conflict. Commitment problems—either
across the two sides to a conflict, or among
factions within a fighting side—are currently
viewed as the leading rationalist theoretical
explanation for civil war, especially for longduration civil wars, although certain types
of information asymmetries may also play
a role. Disentangling the relative contributions of the various commitment problems
and information asymmetries proposed in
the theoretical literature is a top priority for
empirical research. Developing new explanations—possibly challenging the current
modeling assumptions of unitary armed
groups, or even rationality—is also likely to
Second, a variety of theoretical models
predict that low incomes, weak state institutions, and social divisions may contribute
to the onset of civil wars, and these issues
have been the focus of most empirical treatments. The most robust empirical finding in 45 the existing literature is that economic conditions—both low income levels and slow
growth rates—contribute to the outbreak
of civil wars and conflicts in less developed
countries. This finding has found support at
both the cross-country and the micro levels,
although the correct interpretation of these
patterns in terms of underlying theoretical
mechanisms remains contested. A smaller
literature suggests that economic factors are
decisive in driving individual participation in
armed groups. However, the theoretical and
empirical conflict literatures have too often
run along parallel paths, informing each
other, yes, but seldom directly intersecting;
greater efforts need to be made to identify
and test the precise empirical implications of
the leading theoretical frameworks.
In contrast, the empirical evidence that
social divisions, political grievances, and
resource abundance are drivers of violence
remains weaker and more controversial.
The existing literature tends to measure
non-material factors crudely, and empirical
tests rarely attempt to capture the nuances
of a social phenomenon as complex as civil
war, making it impossible to decisively reject
that nonmaterial factors are playing some
role. Further research using better data is
needed to firmly settle the question of what
role political grievances play in driving civil
There is also an emerging literature on the
economic legacies of war. At this point the
macro literature and newer micro literature
have produced somewhat contradictory findings, although they can potentially be reconciled by appealing to the divergent outcomes
they consider. The macro literature focuses
on physical capital, economic growth, and
population, while the micro literature
mainly on human capital. Recall that standard economic growth models, including the
Barro and Sala-i-Martin (2003) framework
described in section 4, predict that the loss of
human capital will have more lasting adverse 46 Journal of Economic Literature, Vol. XLVIII (March 2010) economic growth consequences than the
destruction of physical capital. Future work
must clarify how the nature of the onflict
(internal versus international) as well as the
political, social, and institutional context
affects long-run economic growth, and just
as importantly, must more seriously address
the many omitted variables that could simultaneously drive the outbreak of wars and
affect postwar economic recovery. The neoclassical economic growth framework usefully highlights the most important gap in
our knowledge: the impacts of internal war
on institutions, technology, social norms and
culture. Progress on these issues is critical for
crafting appropriate postwar recovery policies, a major economic policy issue in conflict-prone regions, including ub-Saharan
Throughout this discussion, a key lesson
that emerges is the important role that new
data sources have played in enabling research
progress. The development of the PRIO/
UCDP civil conflict database has propelled
the cross-country conflict literature forward.
Disaggregated data on U.S. bombing patterns
allowed Davis and Weinstein (2002) to carry
out their seminal study on Japan. The increasing number of longitudinal household-level
datasets in less developed countries have
made the new micro studies on war impacts
possible. Some of this data collection has
required remarkable ingenuity and courage
on the part of the investigators, notably, the
collection of data on civilians and combatants
from ongoing or recently concluded wars.
Yet much more work remains to be done. In
our view, a major goal of civil war researchers
within both economics and political science
in the coming years should be the collection
of new data, especially extended panel microdata sets of economic conditions and opportunities. Ideally, these efforts would also be
coordinated, publicly shared and comparable, in a similar fashion, say, to the World
Bank’s Living Standards Measurement Study (LSMS) or the Demographic and Health
Surveys (DHS) program.61
Data collection is of course inherently
difficult in “hot” conflict zones. But even
in many postconflict settings where conditions are closer to normal, statistical agencies simply return to the status quo of survey
instruments, and fail to valuably collect retrospective conflict experience data. To illustrate from the authors’ own experiences in
Liberia, Sierra Leone, and Uganda, neither
the government statistical agencies nor the
international donors financing reconstruction there had plans to systematically include
questions on war experiences, victimization, or participation in the national census
or other representative household surveys
conducted at conflict’s end. Where national
surveys of war experiences were conducted,
they tended to focus exclusively on combatants. Closer cooperation among government
data collection agencies, development organizations, and researchers will be required
for the systematic and comparable data
needed to make further progress.
A few specific data collection directions
appear particularly promising. First, more
detailed information on rebel organization
and decision making would be useful. Some
civil conflicts, like those in Congo and Sudan,
feature a dozen or more active armed groups.
Pooling data from several such settings could
allow for a relatively large sample analysis of
armed groups—or “cross-rebel regressions”—
establishing patterns useful to applied theorists working on rebel organizations. While
the proliferating number of surveys of excombatants (described earlier) will improve
such analysis, so far these datasets have been
selective: most focus on non-state actors and
61 For LSMS, see http://go.worldbank.org/IPLXWM
CNJ0. For DHS, http://www.measuredhs.com. The institutional basis for such coordination may already exist in
the Households in Conflict Network (http://www.hicn.
org). Blattman and Miguel: Civil War
nearly all on Africa. The risk is that our understanding of civil war will be driven by a subset
of conflicts rather than a more globally representative sample. New data from Afghanistan,
Colombia, Indonesia, Iraq, and Nepal (discussed above) is starting to fillin the gaps.
Second, and perhaps easiest to collect, are
follow-up household surveys in post-conflict
settings integrating retrospective information on a wide range of economic behaviors and experiences during the war, along
the lines of the data work in Bundervoet,
Verwimp, and Akresh (2009) in Burundi,
Bellows and Miguel (2006, 2009) in Sierra
Leone, Blattman and Annan (forthcoming) in Uganda, and Verwimp (2005) in
Rwanda. The Burundi and Rwanda surveys
deserve special mention. In both cases the
authors identified a prewar national household survey, located the original (archived)
surveys, and tracked down the sample households again after the war. Such intellectual
entrepreneurship should be expanded and
rewarded in the profession.
Third, we need to improve measures of
political attitudes and grievances and test
their association with actual behaviors. One
example stands out. James Habyarimana et
al. (2007; forthcoming) identify theoretically
distinct mechanisms that link ethnic diversity to trust, cooperation and public goods
provision, and then run experimental games
to compare the explanatory power of the distinct mechanisms in a representative sample
of 300 subjects from a Kampala, Uganda,
slum neighborhood. Experimental economics lab research in other developing countries, especially in conflict and postconflict
societies, could shed light on the individual
decision to participate in violence or on
the resolution of collective action problems
within armed groups.
Fourth, at the macro level, we encourage the development and synthesis of data
on additional forms of political instability
and violence. Political repression figures 47 p
rominently in theories of conflict and cooperation (e.g., Acemoglu and Robinson 2006;
Besley and Persson 2009, forthcoming),
and yet we have a limited sense of its use or
effectiveness. As noted above, the distinction
between civil war and these other phenomena has been asserted rather than demonstrated. If we are interested in the struggle
between groups for national power, it is not
obvious that we should ignore coups; communal violence could similarly shed light on
participation in violent collective action.62
Civil wars and conflicts arguably inflict
more suffering on humanity than any other
social phenomenon. Now they are emerging as central to many countries’ political
evolution and possibly as key impediments
to global development. We hope this article
will promote the incorporation of these topics into graduate and undergraduate courses
in both economics and political science, and
stimulate further research. As we’ve discovered, and to recast Lucas’s famous phrase,
once you start thinking about civil war, it’s
hard to think about anything else.
Abadie, Alberto, and Javier Gardeazabal. 2003. “The
Economic Costs of Conflict: A Case Study of the
Basque Country.” American Economic Review,
Acemoglu, Daron, Georgy Egorov, and Konstantin
Sonin. 2009. “Dynamics and Stability of Constitutions, Coalitions, and Clubs.” Unpublished.
Acemoglu, Daron, Simon Johnson, and James A.
obinson. 2001. “The Colonial Origins of Comparative Development: An Empirical Investigation.”
American Economic Review, 91(5): 1369–1401.
Acemoglu, Daron, and James A. Robinson. 2001. “A
Theory of Political Transitions.” American Economic Review, 91(4): 938–63.
Acemoglu, Daron, and James A. Robinson. 2006. Economic Origins of Dictatorship and Democracy.
Cambridge and New York: Cambridge University
62 New data are already emerging on leadership transitions (Henk E. Goemans, Gleditsch, and Giacomo
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