SOCI 121: Population Problems
Discuss the conceptualization of aging in demography
Discuss the Age Transition
Explain how changes in fertility, mortality, and migration can impact the age structure
Explain how changes in the age structure can impact the major demographic processes
Population Growth and Population Structure
Discussions of population growth often make it seem as though population increases evenly
throughout the population.
But we know that the dynamic population processes – mortality, fertility, and
migration differ by age and sex – these processes affect not only the size, but also the
composition, of the population.
Predictable changes occur in the distribution of a population by age and sex as a
society goes through the demographic transition.
represents a shift away from a very young population in
which there are slightly more males than females to an older population in
which there are more females than males.
In between, fluctuations in the age and sex structure represent
powerful forces for social, economic, and political change – and a
source of demographic change as well.
In general, it is the interaction of fertility, mortality, and migration that
age and sex structure
, which can be viewed as a key to the life
of a social group.
Population processes not only produce the age and sex structure but
are, in turn, affected by it.
The Age Transition
The age transition is a predictable shift from a predominantly younger population when
fertility is high (usually when mortality is high) to a predominantly older population when
fertility is low (usually when mortality is also low).
We know that a premodern world will have high fertility, high mortality, and probably very
little in- or out-migration. This is associated with a young population, whereas the “end” of
the transition is associated with an older population characterized by low fertility, low
mortality, and probably a moderate amount of migration.
Each of the three population processes has predictable impacts on the age structure. Both
migration and mortality can affect all ages and differentially affect each sex. The impact of
fertility is not quite the same, and it is for this reason that changes in fertility tend to have the
most dramatic long-term impact on the age structure. Migration has the biggest short-term