Demography is the branch of the social sciences most directly concerned
with population-related issues. It has been defined as the statistical analysis
of the size, composition and spatial distribution of human populations, and
of changes over time in these aspects through the operation of five
processes: fertility, mortality, marriage, migration and social mobility. Of
these, the study of fertility is dominant ó probably for the reasons outlined
at the beginning of this paper ó and the preoccupation with understanding
the timing, causes and nature of fertility decline explains the central place
given to theories of ìdemographic transitionî within this field of studies.
The kernel of demographic transition theory is the observation that in
Western societies, fertility and mortality were extremely high in the preindustrial
era, and that in contemporary industrial societies they are
extremely low: the demographic transition occurred in between (Demeny,
1974). The attempt to understand the reasons for these changes, the
relationship between different phases and the implications of the Western
experience for contemporary high-fertility societies make up the body of
demographic transition theory (Notestein, 1945; Davis, 1945).