Demographic Transition

The demographic transition theory is a framework used to describe and predict how the population of any region changes over time. It explains the shift from a pattern of high birth rates and high death rates to one of low birth rates and low death rates. This shift happens as a society moves from being rural, agrarian, and illiterate to becoming urban, industrial, and literate. These changes occur in a series of stages, which together are called the demographic cycle.

The theory is typically explained using a three-stage model.

Stage One: High Fertility, High Mortality

In the first stage, both the birth rate (fertility) and the death rate (mortality) are high. People reproduce more to compensate for the many deaths caused by epidemics and an unreliable food supply. As a result, the overall population growth is slow. Most people are engaged in agriculture, where large families are seen as an asset for farm work. Life expectancy is low, the population is largely illiterate, and the level of technology is underdeveloped. Two hundred years ago, every country in the world was in this stage.

Stage Two: Fertility Remains High, Mortality Declines

At the beginning of the second stage, fertility remains high, but it gradually declines over time. The key change here is a sharp reduction in the mortality rate. This decline is driven by improvements in sanitation and health conditions. Because the birth rate stays high while the death rate falls, there is a large gap between them. This gap leads to a very high net addition to the population — in other words, rapid population growth.

Stage Three: Both Fertility and Mortality Decline Considerably …