2. Population change
The demographic transition model
The demographic transition model
The demographic transition model (DTM) describes how the population of a
country changes over time. It plots changes in birth and death rates, and
shows that countries pass through five stages of population change.
4. Population change
The demographic transition model
Stage 1
A period of high birth rate and high death rate, both of which fluctuate.
Population growth is small.
Reasons for the high birth rate include:
• limited birth control/family planning
• high infant mortality rate, which encourages the birth of more children
• children are a future source of income
• in many cultures, children are a sign of fertility
• some religions encourage large families
Reasons for the high death rate include:
• high incidence of disease
• poor nutrition and famine
• poor levels of hygiene
• underdeveloped and inadequate health facilities
5. Population change
The demographic transition model
Stage 2
A period of high birth rate but falling death rate. The population begins to
expand rapidly.
Reasons for the falling death rate include:
• improved public health
• better nutrition
• lower child mortality
• improved medical provision
6. Population change
The demographic transition model
Stage 3
A period of falling birth rate and continuing falling death rate. Population
growth slows down.
Reasons for the falling birth rate include:
• changing socioeconomic conditions
• greater access to education for women
• preferences for smaller families
• changing social trends and fashions, and a rise in materialism
• increased personal wealth
• compulsory schooling, making the rearing of children more expensive
• lower infant mortality rate
• the availability of family planning systems, often supported by
governments
7. Population change
The demographic transition model
Stages 4 and 5
Stage 4
A period of low birth rate and low death rate, both of which fluctuate.
Population growth is small and fertility continues to fall. There are significant
changes in personal lifestyles. There are more women in the workforce, high
personal incomes and more leisure interests.
Stage 5
A period during which the death rate slightly exceeds the birth rate. This
causes population decline.
Reasons for the low birth rate include:
• a rise in individualism, linked to women working
• greater financial independence of women
• concern about the impact of increased population numbers on the
resources for future generations
• an increase in non-traditional lifestyles, such as same-sex relationships
• a rise in the concept of childlessness
8. Population change
The demographic transition model
The link between the DTM and age–sex structure
The demographic transition model can be used to demonstrate changes
in age–sex structure spatially and over time. This can be seen in the
characteristic shapes and names of population pyramids at each stage
of the population DTM.
• Stage 1 (high fluctuating) High birth rate, rapid fall in each upward age
group due to high death rate, short life expectancy.
• Stage 2 (early expanding) High birth rate, fall in death rate so more
middle-aged people alive, slightly longer life expectancy.
• Stage 3 (late expanding) Declining birth rate, low death rate, more
people living to an older age.
• Stage 4 (low fluctuating) Low birth rate, low death rate, higher
dependency ratio, longer life expectancy.
10. Population change
The demographic transition model
The link between the DTM and age–sex structure
Mexico, 2000
Sweden, 2000
Source: US Census Bureau, International Data Base.
