Demographic Transition Model

The demographic transition model explains how populations tend to move from high birth and death rates to low birth and death rates as societies undergo socioeconomic change. Its central insight is that death rates usually decline before birth rates, creating a temporary phase of rapid population growth.

Core logic of the transition

Improvements in food supply, sanitation, public health and medical care first produce a mortality decline. The subsequent fertility decline is associated with urbanisation, education, lower infant mortality and deliberate preference for smaller families. The changing gap between births and deaths determines the rate of natural increase.

Stages of demographic transition

• In Stage I, birth and death rates are both high, so population growth is slow and may fluctuate.
• In Stage II, death rates fall rapidly while birth rates remain high initially and decline later, producing high population growth.
• In Stage III, both birth and death rates are low and close to balance, so the population becomes stable or grows slowly.

Interpretive value and limits

The model presents a broad historical sequence rather than a fixed timetable. The timing and speed of transition vary across societies according to their economic, social and institutional conditions. Since the model focuses on births and deaths, migration must be considered separately when explaining actual population change.