The Demographic Transition Model and Development

How development changes population growth

Development involves changes in people's living conditions as well as changes in the economy. More reliable food supplies, cleaner water and better medical care can all affect how many people survive. Changes in society also affect how many children people have.

The Demographic Transition Model (DTM) connects these changes. It shows the general pattern of birth rates and death rates as societies develop and industrialise. A birth rate measures live births per 1,000 people each year; a death rate measures deaths on the same basis, so the two can be compared directly.

When births outnumber deaths, there is natural increase. When deaths outnumber births, there is natural decrease. These describe change through births and deaths only: migration can also change a country's population.

Reading the relationship between the lines

On a DTM graph, follow the birth-rate and death-rate lines together. When the birth-rate line is above the death-rate line, the population grows naturally. A wider vertical gap means faster natural increase. When the lines are close together, natural change is small. If the birth-rate line falls below the death-rate line, there is natural decrease.

Neither line shows the total number of people. A population can therefore continue growing even while its birth rate falls, provided births still outnumber deaths.

Stage 1: high birth and death rates

Stage 1 represents a pre-industrial society with a low level of development. Both birth rates and death rates are high. Because many births are balanced by many deaths, natural increase is small and the population remains relatively stable.

Poor diets, food shortages and limited healthcare contribute to high death rates. Infant mortality—deaths among children before their first birthday—is high, so families may have more children in the hope that some survive to adulthood. Limited access to contraception also helps keep birth rates high.

The important distinction is between high rates and rapid growth: a high birth rate alone does not produce rapid growth if the death rate is also high.

Stage 2: living conditions improve before birth rates fall

As development begins, food becomes more reliably available, water supplies become cleaner, and sanitation and medical care improve. These changes reduce deaths, including deaths among infants, so the death rate falls. Stage 2 is commonly associated with lower-income countries where basic living conditions are improving.

The birth rate remains high for a time. Changes in family behaviour do not happen immediately when survival improves: there is a lag before birth rates decline. In economies where agriculture provides many jobs, children can also help with farm work, encouraging larger families. The resulting large gap between births and deaths produces rapid natural increase.

This explains why early improvements in development can make population growth faster rather than slower. The first major change is that more people survive.

Stage 3: birth rates fall and growth slows

As society develops further and adjusts to urban and industrial life, the birth rate begins to fall. Several connected changes encourage smaller families:

• Improved child survival: parents become more confident that their children will reach adulthood.
• Access to contraception and family planning: people have greater control over whether and when they have children.
• Women's education and employment: wider opportunities can encourage later childbearing and smaller families.
• Changing work and family costs: as manufacturing becomes more important, there is less need for children to work on farms, while raising children becomes more costly.

Stage 3 is often associated with industrialising economies, including newly emerging economies. Healthcare continues to improve, but the death rate is already relatively low, so its decline is slower. The falling birth rate narrows the gap between births and deaths.

Population still increases while births outnumber deaths, but the rate of natural increase slows. Towards the end of this stage, births and deaths approach a balance. A slowing rate of growth is therefore different from population decline.

Stage 4: low rates and greater stability

In Stage 4, both birth and death rates are low and broadly balanced. Natural increase is small, and the population becomes relatively stable again. This stage is generally associated with higher-income countries.

Good healthcare, reliable food supplies and high living standards help keep death rates low. Low infant mortality, accessible contraception and education support low birth rates.

Stage 4 differs fundamentally from Stage 1. Both have little natural change, but Stage 1 has high birth and death rates whereas Stage 4 has low rates. In the model, the population is also much larger after the growth experienced during the transition.

Stage 5: births fall below deaths

Some highly developed countries reach Stage 5, where the birth rate is below the death rate. This produces natural decrease.

Birth rates remain very low as people have fewer children and may delay starting families. Meanwhile, low birth rates and longer lives create an ageing population, with older people forming a larger share of the total. The death rate may rise slightly because more people are in older age groups, even though healthcare remains good. This is not a return to the poor living conditions of Stage 1.

Japan is an example commonly used to illustrate Stage 5 and an ageing population. Natural decrease does not necessarily mean that a country's total population falls: migration also affects the total.

Using the model to understand development

The overall connection is that improving living conditions first reduces death rates; birth rates fall later as society changes. Population growth speeds up during the gap between these changes, then slows as the rates converge. If births fall below deaths, natural decrease follows.

The DTM describes a general transition, not an exact schedule. Use the pattern of both rates and the changes in living conditions to explain a stage, rather than assuming that a country's income alone fixes its position in the model.

Rates and natural change

• Birth and death rates: per 1,000 people per year.
• Births exceed deaths → natural increase.
• Deaths exceed births → natural decrease.
• The vertical gap between the rates shows the rate of natural change, not population size. Migration is excluded.

Development through the transition

Essential links

• Death rates fall first as survival improves.
• Birth rates fall later: better child survival, contraception, women's education and employment, and less need for children as farm workers.
• Stages 1 and 4 both have little natural change, but very different rates and living conditions.
• In Stage 5, ageing can raise the death rate slightly despite good healthcare.
• The DTM is a general model, not a fixed timetable.