Demographic Transition Model

A model that defines four progressive stages of demographic development, in an attempt to elucidate and analyze the various conditions and factors that influence population growth. Some sources use the term “demographic transformation” to refer to this model. The key relationship at the center of the model is the dynamic between death rates and birth rates, and how these are altered by changing socioeconomic conditions over time. In particular, the model relates increasing rates of economic advancement and higher levels of urbanization to a general, and at least in theory, long-term, reduction in population growth. The model is based on the experience of economically advanced countries that underwent industrialization in the late 19th and early 20th centuries.

The first stage of the model, typically called the “preindustrial” stage or “high stable” stage, is marked by both high birth rates and high death rates. The total fertility rate and infant mortality rate are also both quite high, compared to later stages of the model. Life expectancy for both genders is also typically reduced in comparison to subsequent stages, due to the influence of food shortages, disease, and frequent violent conflict. Population growth in this stage is generally low, because while the birth rate may exceed the death rate for a short interval, it is also just as likely for the death rate to be higher, and neither is marked by a sustained trend upward. The age structure of the population at this stage is typically youthful, with large numbers of individuals in the lower-age cohorts, and few in the older cohorts, reflecting the high rates of birth, fertility, and mortality, as few people survive into “old age.” Represented by a population pyramid, a country or region in this stage would show a pyramid with a broad base (high birth rate) tapering steeply to a sharp pinnacle (high death rate). Few countries are considered to be currently at this stage of the model.