Global Diversity

World Health Trends

World health research considers global patterns of interaction between people, products, money and information as they affect health trends.

Learning Objectives

Explain why health interventions must not just address diseases but also structural factors

Key Takeaways

Key Points

  • Global illnesses are often classified into the categories " diseases of affluence " and " diseases of poverty," reflecting the impact of national economic development on health conditions and outcomes.
  • Diseases of affluence refer to physical and mental health conditions for which personal lifestyles and societal conditions associated with economic development are believed to be an important risk factor, and they include many non-communicable diseases.
  • Diseases of poverty are usually infectious diseases that are often related to poor sanitation, low vaccination coverage, inadequate public health services, and weak enforcement of environmental health and safety regulations.
  • Because health trends are impacted by social, economic, and political conditions, global health interventions must address not just diseases themselves, but also the structural factors which prevent certain groups from accessing adequate healthcare.

Key Terms

  • diseases of poverty: A group of conditions largely consisting of infectious diseases that are related to poor sanitation, low vaccination coverage, and inadequate health and safety regulations.
  • World Health Organization (WHO): A specialized agency of the United Nations (UN) that is concerned with international public health.
  • diseases of affluence: Refers to diseases that are caused by personal lifestyles and social conditions associated with affluence, such as high fat diets and environmental pollution.

As flows of people, money, products, and information increasingly transcend national boundaries, it becomes important to study health trends not just within nations, but from a worldwide perspective. World (or global) health as a research field emerged out of this necessity and lies at the intersection of the medical and social science disciplines, including the fields of demography (the study of population trends), economics, epidemiology (the study of the distribution of health events in a population), political economy, and sociology.

Historically, global health studies rose to prominence in the 1940s, after World War II reconfigured geopolitical alignments and international relations. In 1948, the member states of the newly formed United Nations gathered together to create the World Health Organization (WHO). The organization began with a focus on prevention and eradication of contagious diseases, such as cholera, smallpox, and malaria. WHO initiatives have evolved and expanded throughout the years, however. For example immunization initiatives were launched in the 1970's, HIV/AIDs initiatives in the 1980's, and violence awareness initiatives in the 2000's. While the WHO is the key international agency for monitoring and promoting global health, many other groups also participate.

Diseases of Affluence and Diseases of Poverty

The main diseases and health conditions prioritized by global health initiatives are sometimes classified under the terms diseases of affluence and diseases of poverty, although the impacts of globalization are increasingly blurring any such distinction.

Diseases of affluence refer to physical health conditions for which personal lifestyles (such as lack of exercise or eating a high-fat diet) and societal conditions (such as stressful work arrangements or environmental pollution) associated with economic development are believed to be an important risk factor. Examples of diseases of affluence include Type II diabetes, asthma, coronary heart disease, obesity, hypertension, cancer, and alcoholism. Depression and other mental health conditions may also be included as conditions associated with increased social isolation and lower levels of psychological well being observed in many developed countries. Many of these conditions are interrelated. For example, obesity can be linked to many other illnesses and deaths in high-income nations.

So-called diseases of affluence are predicted to become more prevalent in developing countries, as diseases of poverty decline, longevity increases, and lifestyles change. In 2008, nearly 80% of deaths due to non-communicable diseases, including heart disease, strokes, chronic lung diseases, cancers, and diabetes, occurred in low- and middle-income countries.

In contrast, the diseases of poverty tend to consist largely of infectious diseases, often related to poor sanitation, low vaccination coverage, inadequate public health services, and weak enforcement of environmental health and safety regulations. At the global level, the three primary poverty-related diseases are AIDS, malaria, and tuberculosis. Developing countries account for 95% of the global AIDS prevalence and 98% of active tuberculosis infections. Furthermore, 90% of malaria deaths occur in sub-Saharan Africa. Together, these three diseases account for 10% of global mortality.

Treatable childhood diseases are another set of illnesses that are seen at disproportionately high rates in poor countries, despite the existence of cures for the diseases for decades. These illnesses include measles, pertussis, diarrheal diseases, pneumonia, and polio. Among children under the age of 5 in the developing world, malnutrition, which results from either a lack of food or an inadequately diversified diet, contributes to 53% of deaths associated with infectious diseases. Malnutrition impairs the immune system, thereby increasing the frequency, severity, and duration of childhood illnesses. Micronutrient deficiencies also compromise intellectual potential, growth, development, and adult productivity.

Health Interventions


Maternal health clinic in Afghanistan: Maternal health is one of the priorities of global health organizations, such as the World Health Organization.

As the above discussion of diseases of poverty and diseases of affluence reveals, health trends are closely related to social, political, and economic patterns. Thus, health interventions must likewise address not just diseases themselves, but the structural factors which prevent certain groups from accessing adequate healthcare or from having adequate information with which to practice healthy habits and prevent disease. These interventions could include addressing issues of structural inequality, that is, the highly unequal distribution of global wealth that results in conditions of extreme poverty which are difficult if not impossible to escape. It could also mean addressing the global economic patterns which result in healthcare workers having more incentive to work in developed countries and leaving developing countries short staffed. Finally, health interventions could advance by considering the relationship of national and international politics to the establishment of adequate education and healthcare systems.

Hunger, Malnutrition, and Family

Those with weak support structures are more vulnerable to hunger and starvation than those with strong family networks.

Learning Objectives

Describe different attempts to understand world hunger

Key Takeaways

Key Points

  • Globally, hunger, malnutrition, starvation, and related health problems cause a significant number of deaths, particularly in the developing world.
  • Conflicting perspectives on global hunger attribute the problem to food shortages, poor food distribution, and economic policies that favor export over local consumption.
  • Amartya Sen won his 1998 Nobel Prize, in part for his work in demonstrating that hunger in modern times is not typically the product of a lack of food, but rather of problems in food distribution networks and governmental policies in the developing world.

Key Terms

  • Malthusianism: The idea that population growth will outpace food production, resulting in widespread famine and population reduction.
  • food sovereignty: A policy framework advocated for by a number of farmers, peasants, pastoralists, fisherfolk, indigenous peoples, women, rural youth, and environmental organizations, which consists of the right of peoples to define their own food, agriculture, livestock, and fisheries systems, in contrast to having food largely subject to international market forces.

"Hunger" is the most commonly used term to describe the social condition of people who frequently experience the physical sensation of desiring food. "Malnutrition" is a general term for conditions caused by improper diet or nutrition, and can occur in conjunction with under- or overconsumption of calories. Undernutrition is the result of chronic underconsumption of food.

Two terms frequently associated with hunger are "famine" and "starvation. " Famine is the widespread scarcity of food, and it is usually accompanied by regional malnutrition, starvation, epidemic, and increased mortality. Starvation describes a state of exhaustion of the body caused by lack of food and may be fatal.

World Statistics

While statistics vary based on measurements used, it is generally agreed that the number of malnourished or undernourished people in the world was around 1 billion people in 2010, about a sixth of the world's total population. Hunger is particularly devastating for children. Approximately six million children die of hunger every year.


Hunger: This map shows the percentage of a country's population that is undernourished.

Understanding Hunger

Attempts to understand why hunger exists are not new. Thomas Malthus, in the six editions of his book, An Essay on the Principle of Population, published from 1798 to 1826, argued that the explosive population growth happening in his time could not continue indefinitely. He claimed population growth would eventually be checked by famine and disease, because the earth's ability to produce food would not be able to keep up with the size of the population. His dire predictions are widely known as "Malthusianism. "

Current population growth, which is still on the rise, seems to disprove Malthus' theory, hunger problems notwithstanding. In fact, many believe that the earth is more than capable of sustaining the current world population. The Food and Agricultural Organization of the United Nations purports that the world already produces enough food to feed everyone–over 6 billion people–and could feed double that number of people. Amartya Sen won his 1998 Nobel Prize in part for his work in demonstrating that hunger in modern times is not typically the product of a lack of food, but rather problems in food distribution networks and governmental policies in the developing world.

Today, there is a wide range of opinions as to why the hunger problem is so persistent. Some organizations raise the issue of food sovereignty and claim that every country on earth (with the possible minor exceptions of some city-states) has sufficient agricultural capacity to feed its own people, but that the free trade economic order prevents this from happening. These advocates argue that free trade policies transfer economic decision-making power into the hands of multilateral organizations, such as the World Bank and International Monetary Fund and transnational corporations, so that local people are unable to determine what is done with food that is locally produced.

At the other end of the spectrum, transnational organizations like the World Bank claim to be part of the solution to hunger, maintaining that the best way for countries to succeed in breaking the cycle of poverty and hunger is to build export-led economies that will give them the financial means to buy foodstuffs on the world market.

The Role of the Family in Hunger Problems

The family plays an important role in understanding patterns of hunger. Those who have a weak or non-existent family support structure are more likely than those with strong family networks to go hungry. Children and seniors are the most vulnerable to going hungry for lack of familial support.

Children, since they are less able to provide for themselves than adults, are more likely to go hungry if they live in unstable families or on the streets. Malnutrition and hunger-related diseases cause (at least partially) 60% of children's deaths in the developing world.

Seniors are another at-risk population for hunger. According to one 2007 study, over 11.4% of seniors in the United States experience some form of food insecurity. The most at-risk segments of the senior population include those who lack a strong family structure (i.e., those who were never married), live alone, or live with a grandchild (but with no adult child present).

The Health of Infants and Children

Childhood mortality is high in developing countries where malnutrition, infectious diseases, and unsanitary conditions are widespread.

Learning Objectives

Describe the most common causes of child mortality

Key Takeaways

Key Points

  • International organizations have worked to improve maternal and childhood health conditions around the world, and have helped to reduce the number of childhood deaths from 17 million annually in the 1980s to 10 million annually in the 2000s.
  • Without diagnosis and treatment, about 35% of HIV-infected pregnant women will transmit HIV to their infants. As a result, approximately 1,000 HIV-infected children are born every day.
  • Birth defects are among the leading global causes of infant and child mortality, with an estimated 4.9 million birth defect pregnancies worldwide each year. The majority of these occur in low- and middle- income countries.
  • The World Health Organization has estimated that about 1.5 million children under age 5 years continue to die annually from diseases that are preventable via the administration of vaccines, making up approximately 20% of overall childhood mortality.
  • Spreading technology, health information, and nutrition and medication may held reduce rates of infant and child mortality in developing countries.

Key Terms

  • dengue: An acute febrile disease of the tropics caused by a flavivirus, transmitted by mosquitoes, and characterized by high fever, rash, headache, and severe muscle and joint pain.
  • birth defect: Any of several medical disorders that are present at birth.
  • Diarrheal Diseases: The condition of having three or more loose or liquid bowel movements per day, which is a common cause of death in developing countries and the second most common cause of infant deaths worldwide.

In the 1980's, the United States increased funding for maternal and childhood health programs. At that time, it was estimated that 17 million children under the age of 5 died every year. By 2006, largely due to the efforts of many international aid organizations, the annual number of deaths of children under the age of 5 was 10 million. Even with the great advances in childhood health that have occurred in recent decades, many health problems still afflict infant and child populations.


Without diagnosis and treatment, about 35% of HIV-infected pregnant women will transmit HIV to their infants. As a result, approximately 1,000 HIV-infected children are born every day, accounting for about 370,000 new pediatric infections annually, 85% of which are in 25 sub-Saharan African countries. Without antiretroviral drugs, half of these children die by age 2. Of the estimated 2.3 million children worldwide with HIV, 1.27 million are estimated to need treatment and only 356,000 (28%) receive it.

Birth Defects

Birth defects are among the leading global causes of infant and child mortality, with an estimated 4.9 million birth defect pregnancies worldwide each year. The majority of these occur in low and middle income countries.

Birth defect trends and risk factors are difficult to monitor because many countries do not have systems that can accurately track the prevalence of birth defects. International organizations have been working to expand monitoring systems and improve laboratory capacity. In the United States, the Centers for Disease Control and Prevention researches and tracks birth defects and coordinates the surveillance and research activities of about 40 member programs of the International Clearing House for Birth Defects Surveillance and Research.

Infectious Diseases

In Asia, dengue fever, an infectious tropical disease, is a major cause of child mortality. Global research teams have been working to improve methods for diagnosing and treating dengue. A 2011 CDC report found that the incidence of dengue has increased worldwide in recent decades, but little is known about its incidence in Africa.

Diarrheal diseases cause an estimated 1.4 million deaths per year in children under 5 years old. In developing countries, diarrheal diseases are also a leading cause of death from infections among persons with HIV. Lack of access to water and sanitation and poor hygiene are responsible for most of these deaths. Poor nutrition is also an important factor in diarrheal disease risk.

The World Health Organization has estimated that about 1.5 million children under age 5 years continue to die annually from diseases that are preventable via the administration of vaccines, making up approximately 20% of overall childhood mortality. Vaccines can prevent pneumonia and diarrhea, the two leading causes of death among children under age 5. Other immunizations that can improve maternal and child health are tetanus immunization of pregnant women and polio immunization. Moreover, an estimated 4 million newborns die in the first four weeks of life, accounting for 40% of all deaths among children under the age of 5. Improved pre- and post-natal care, as well as more accessible information about infant health, could help reduce the infant mortality rate.


Child Hunger and Infection: Hunger is one of the basic needs of a human, or on the ERG, a need of existence.


Infant mortality rates are reduced by increasing availability of safe emergency pregnancy care and training doctors and nurses to promote safe breast feeding for HIV infected women and other support and guidance related to pregnancy, delivery, and postpartum periods. Globally, untreated maternal syphilis still causes more than 650,000 adverse pregnancy outcomes, including about 350,000 pre-birth deaths, each year. The overwhelming majority of these are in countries with limited laboratory capacity for syphilis testing as part of basic pregnancy care. Congenital syphilis, passed from mother to child, can be eliminated through universal screening of pregnant women early in pregnancy, and prompt treatment with at least one injection of penicillin. International organizations are working to make these interventions available.


African American Midwives and Infant Mortality: This poster from a museum exhibit illustrates how in impoverished communities without access to technologically advanced medical facilities, the first intervention used to reduce rates of infant mortality is often improving sanitation or hygienic standards.


HIV/AIDS results in high infection and mortality rates amidst inadequate distribution of preventative information and treatment.

Learning Objectives

Describe how HIV/AIDS affects different regions on a global scale

Key Takeaways

Key Points

  • HIV/AIDS is primarily transferred through sexual contact, blood transfusions and needle sharing, and mother-child contact during pregnancy, birth, and breastfeeding.
  • HIV/AIDS has disproportionately impacted low-income countries in sub-Saharan Africa and Southeast Asia, with high proportions of infected women and children and low access to adequate healthcare and anti-retroviral drugs there.
  • Governmental and non-profit organizations have developed to improve HIV/AIDS prevention, treatment, and social services, but many populations continue to be ravaged by the disease.

Key Terms

  • pandemic: A disease that hits a wide geographical area and affects a large proportion of the population.

Human immunodeficiency virus infection / acquired immunodeficiency syndrome (HIV/AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). The illness interferes with the immune system, making people with AIDS much more likely to get infections, including opportunistic infections and tumors that do not usually affect people with working immune systems. This susceptibility increases as these disease gets worse.

HIV is transmitted primarily via sexual intercourse (including oral sex and anal sex), contaminated blood transfusions and hypodermic needles, and from mother to child during pregnancy, delivery, or breastfeeding. Prevention of HIV infection, primarily through safe sex and needle-exchange programs, is a key strategy to control the disease. There is no known cure for or vaccine against HIV, but antiretroviral treatment can slow the course of the disease and may lead to a near-normal life expectancy for people with HIV. Antiretroviral treatment reduces the risk of death and complications from the disease. However, these medications are expensive and may be associated with side effects of their own.

HIV/AIDS and World Health

HIV/AIDS is a major health problem in many parts of the world, and is considered a pandemic—a disease outbreak which is present over a large area and is actively spreading. In 2009, the World Health Organization (WHO) estimated that there are 33.4 million people worldwide living with HIV/AIDS, with 2.7 million new HIV infections per year and 2.0 million annual deaths due to AIDS. Of the approximately 34 million people infected with HIV/AIDS, approximately 16.8 million are women and 3.4 million are younger than 15 years old. AIDS was first recognized by the Centers for Disease Control and Prevention (CDC) in 1981 and its cause, HIV, was identified in the early 1980s.


Map of AIDS Prevalence Among Young Adults: AIDS prevalence is distributed unequally across the world, with sub-Saharan Africa and Southeast Asia experiencing the worst of the pandemic.

Sub-Saharan Africa is the region most affected by the global HIV/AIDS pandemic. In 2010, an estimated 68% (22.9 million) of all HIV cases and 66% of all deaths (1.2 million) occurred in this region. About 5% of the sub-Saharan African adult population is infected and HIV/AIDS is believed to be the cause of 10% of all deaths in children. Women compose nearly 60% of cases in the region. South Africa has the largest population of people with HIV of any country in the world, at 5.9 million.

South and Southeast Asia is the second most affected region in the world. In 2010, this region had an estimated 4 million cases, or 12% of all people living with HIV, resulting in approximately 250,000 deaths. Approximately 2.4 million of these cases are in India.

Prevalence is lowest in Western and Central Europe at 0.2% and East Asia at 0.1%. In 2008 in the United States, approximately 1.2 million people were living with HIV, resulting in about 17,500 deaths. The CDC estimated that in 2008 20% of infected Americans were unaware of their infection.


Many international organizations are working to reduce the spread of HIV/AIDS and its mortality rate. Campaigns have attempted to distribute condoms to HIV/AIDS stricken regions–consistent condom use reduces the risk of HIV transmission by approximately 80% over the long-term. Circumcision in sub-Saharan Africa has been found to reduce the risk of HIV infection in heterosexual men by between 38% and 66% over two years. Based on these studies, the World Health Organization has recommended male circumcision as a method of preventing female-to-male HIV transmission. Additionally, early treatment of HIV-infected people with antiretrovirals protected 96% of sexual partners from infection.


People infected with HIV/AIDS can be treated with anti-retroviral drugs. This medication can relieve many of the symptoms associated with the infection, such as increased susceptibility to other viral infections. Moreover, benefits of treatment include a decreased risk of progression from HIV to AIDS and a decreased risk of death. Medication can also include a decreased risk of transmission of the disease to sexual partners and a decrease in mother to child transmission. However, these drugs often have significant side effects and they are expensive, making them difficult to access in low-income countries.

Population Trends

The world population has been growing continuously since the 14th century, but the growth rate has been decreasing in the last few decades.

Learning Objectives

Evaluate scenarios of over and underpopulation

Key Takeaways

Key Points

  • The demographic transition describes countries' shifts from high population growth— fueled by high birth rates and low death rates—to population stability or shrinkage— brought about by low birth and death rates. This transition occurs in tandem with economic development.
  • Human overpopulation is a state where the population exceeds the available material and social resources; underpopulation occurs when the birth rate is not sufficient to maintain a stable population.
  • Overpopulation can lead to many problems, including famine, disease, conflict, and underdevelopment of national economic and social potential; underpopulation can lead to reductions in the GDP and slowed economic growth.
  • Proposed solutions to global overpopulation include a survival of the fittest attitude, economic development to stimulate the demographic transition in countries with growing populations, and a combination of population control and self-sufficiency methods.

Key Terms

  • Malthusianism: The idea that population growth will outpace food production, resulting in widespread famine and population reduction.
  • demographic transition: The shift from high birth rates and death rates to low birth rates and death rates, usually occurring alongside economic development.
  • laissez-faire: Describes a policy of governmental non-interference in economic affairs.

The world population has experienced continuous growth since the end of the Great Famine and the Black Death in 1350, when it stood at around 370 million. Between October 2011 and March 2012, it was estimated that the world population exceeded 7 billion. The world population growth rate was estimated at 1.1% per year as of 2011, a rate which has declined since its peak during the 1950s–1970s.

The Demographic Transition

Despite an overall pattern of growth, population trends are not even across countries. The demographic transition helps explain the differences between countries. The demographic transition refers to the shift from high birth rates and death rates to low birth and death rates; this occurs as part of the economic development of a country. The basic premises of the theory are as follows: in pre-industrial societies, population growth is relatively slow because both birth and death rates are high; as countries develop, death rates fall faster than birth rates do, resulting in large population growth; as development stabilizes, birth rates drop off and the population stabilizes.


The Demographic Transition: This model illustrates the demographic transition, as birth and death rates rise and fall but eventually reach equilibrium.

Overpopulation at a National Level

Overpopulation indicates a scenario in which the population of a living species exceeds the carrying capacity of its ecological niche. Overpopulation is not a function of the number or density of the individuals, but rather the number of individuals compared to the resources they need to survive. In other words, it is a ratio—population:resources. Resources important in measures of overpopulation include clean water, food, shelter, healthcare, etc.

Most of the population growth in the world today comes from developing countries, most notably African countries, where birth rates have remained high. Many of these countries are struggling to provide food and resources necessary to support a young, growing population. Overpopulation can result in a variety of problems, including famine, shortage of natural resources, spread of communicable disease due to dense populations, and conflict over scarce resources.

Underpopulation at a National Level

Once countries pass through the demographic transition, some experience fertility rate decreases so substantial that they fall well below replacement level—the birth rate needed to maintain a stable population—and their populations begin to shrink. About half the world population lives in nations with sub-replacement fertility. A new fear for many governments, particularly those in countries with very low fertility rates, is underpopulation—a state in which the declining population reduces the GDP and economic growth of the country, as population growth is often a driving force of economic expansion. To combat extremely low fertility rates, some of these governments have introduced pro-family policies, such as payments to parents for having children and extensive parental leave for parents.

Debates about Overpopulation on a Global Level

Despite concerns of underpopulation in individual countries, overpopulation is still the most pressing concern for those who track global population trends. Presently, the world's population grows by approximately 80 million annually. The United Nations projects that the world population will stabilize in 2075 at nine billion due to declining fertility rates.

Concerns about overpopulation are not new; early in the 19th century, Thomas Malthus argued in "An Essay on the Principle of Population" that, if left unrestricted, human populations would continue to grow until they would become too large to be supported by the food grown on available agricultural land. Once the population exceeded the planet's carrying capacity, the population would be restrained through mass famine and starvation. Malthus argued for population control—policies intended to lower the birth rate—to avoid this happening. His arguments are widely known as Malthusianism, and present-day proponents of this theory are called Neo-Malthusians. Critics of Malthus point to the fact that the widespread famines he predicted have not occurred, even though the world population has continued to expand.

Possible Solutions to Overpopulation

Some approach overpopulation with a laissez-faire attitude, arguing that if the earth's ecosystem becomes overtaxed, it will naturally regulate itself. In this mode of thought, disease or starvation are natural means of decreasing the population. Objections to this argument include that a huge number of plant and animal species would go extinct; terrible pollution would arise in some areas, and it would be difficult to abate; and moral problems would be created—great suffering for the people who do not have access to resources.

Others argue that economic development is the best way to reduce population growth because economic development can spur demographic transitions that lead to reduced fertility rates. Where women's status has improved, for example, there has generally been a drastic reduction in the birth rate, resulting in more sustainable growth levels.


Population Growth According to Development: The majority of world population growth today is occurring in less developed countries.

Global Aging

On average, global life expectancies have been increasing and birth rates declining, resulting in global aging.

Learning Objectives

Examine aging as a global issue

Key Takeaways

Key Points

  • Developments in healthcare, lifestyle, and political stability have led to longer life expectancy worldwide.
  • While global life expectancy is increasing, the rate at which the world population is aging is not uniform across countries—life expectancies are higher in wealthier, developed countries than in poorer, developing ones.
  • Growing life expectancy is not the only factor contributing to global aging. As nations develop, average birth rates decline.
  • As more people in a nation's population reach old age, the nation's healthcare and social security system will be strained.

Key Terms

  • life expectancy: The amount of time one is expected to live.
  • life span: the length of time for which a person lives, or for which something exists or is current or valid

Globally, most countries are seeing the average life expectancy of their populations increase. This trend translates to a greater percentage of the world's population over the age of 65. However, the rate at which the world's population is aging is not uniform across the world—some countries have actually seen decreasing life expectancies.

Economic circumstances are one factor that affects life expectancy. Citizens living in wealthier, more developed countries or regions tend to have higher life expectancies. For example, in the United Kingdom, life expectancy in the wealthiest areas is several years longer than in the poorest areas. Wealth may be correlated to factors such as diet and lifestyle as well as better access to medical care—many wealthy European countries offer universal healthcare. As more people in a nation's population reach old age, its healthcare and social security system will be strained. This strain is occurring in the United States, where people born into the baby boomer generation of the 1950s–1960s are aging and reaching retirement age, thus tapping into Medicaid and social security funds at unprecedented rates.

People living in poorer, less developed countries tend to have lower life expectancies. Much of the higher death rates in poorer nations is due to war, starvation, infant deaths, diseases, and lack of access to adequate health care. The presence of one risk factor is often related to another—war torn countries, for example, are likely to have more instances of starvation. Likewise, people with diseases may have a difficult time getting or sustaining a job, making them vulnerable to starvation. The impact of AIDS on life expectancy is particularly significant in many sub-Saharan African countries. As nations develop, their life expectancy generally rises.

Growing life expectancy is not the only factor contributing to global aging. As nations develop, the average number of children per parent drops. There are several possible reasons for this trend: first, in poorer countries, it may be important to have many children because infant mortality is high and children provide financial support for households and support for their parents in retirement. As a population gets richer, these reasons will become less important. Second, as women become more educated, they tend to delay having children until later in life. This naturally leads to fewer childbirths.

A drop in the birth rate means that the percentage of people in a society who are young will decline. This, combined with higher life expectancies, means that the ratio of old to young people will grow and the population as a whole will age. These two trends, stemming from the growing global economy, cause global aging.


Percentage of Population Above 65: 2005: This map illustrates global trends in aging by depicting the percentage of each country's population that is over the age of 65. More developed countries have older populations because their citizens live longer. Less developed countries have much younger populations.

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