demographic transition
Summary
The demographic transition is the shift of a society from high birth and death rates to low birth and death rates as it industrializes. Death rates usually fall before birth rates, so population growth is fastest in the middle stage, when the gap between the two is widest.
Detail
Meaning: The demographic transition is the shift of a society from high birth and death rates to low birth and death rates as it industrializes. Death rates usually fall first (sanitation, nutrition, medicine). Birth rates fall later (urbanization, women's education, contraception, lower child mortality). The lag causes rapid growth. Stages: 1, both rates high, slow growth; 2, death rate falling, rapid growth; 3, birth rate falling, growth slowing; 4, both low, growth near zero. Some versions add a fifth stage with births below deaths.
Equation: Natural increase rate = CBR − CDR, where CBR is the crude birth rate and CDR is the crude death rate, each in events per 1,000 people per year.
On the MCAT: Passages show birth and death rate curves or population pyramids and ask which stage a country is in. Growth is greatest where the gap between the curves is widest, usually stage 2. A wide-based pyramid fits stage 2; a more columnar one fits stage 4.
Common confusion: Growth does not peak when the birth rate is highest; it tracks birth rate minus death rate. The term is also not the epidemiological transition, which is the shift in leading causes of death from infectious to chronic disease.
Sources
- Introduction to Sociology
- Sociology
- Sociology: A Brief Introduction
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.