AP® Human Geography review sheet from Aim for Five (aimforfive.com/geo/units/2/2-5)
Unit 2 · Topic 2.5
2.5 The Demographic Transition Model
The demographic transition model (DTM) describes how birth and death rates change as a country develops, and the epidemiological transition explains why the main causes of death change. Both are useful, but both have limits you need to explain.
Key terms
- demographic transition model (DTM)
- epidemiological transition model
- infectious disease
- chronic (degenerative) disease
- zero population growth
The five stages
No country is in Stage 1 today. Countries with very high birth rates and falling death rates, such as Niger and Chad, fit Stage 2. Many countries in North Africa, South Asia and parts of Sub-Saharan Africa, such as Kenya, are in Stage 3. The U.S. and most of Europe are in Stage 4. Japan, Italy and South Korea have more deaths than births, which some geographers call Stage 5. Stage 5 was added later and isn't part of the original model.
| Stage | Birth rate | Death rate | Growth | Why |
|---|---|---|---|---|
| 1 | High | High, swings up and down | Very slow | Famine, disease and poor sanitation keep deaths high; children are needed for work |
| 2 | High | Falling fast | Rapid | Better food supply, clean water, sanitation and vaccines lower deaths, while births stay high |
| 3 | Falling | Low | Slowing but still positive | Urbanization, women's education and jobs, and contraception lower births |
| 4 | Low | Low | Near zero | Small families are the norm; the population is older |
| 5 | Very low | Rising slightly | Negative | Births fall below deaths in a very old population |
What the stages mean for pyramids
The DTM lines up with the pyramid shapes from topic 2.3. Stage 2 gives a wide-based, fast-growing pyramid. By Stage 4 the sides are fairly straight, and Stage 5 gives a narrow base and a wide top. Zero population growth is reached when births plus immigration equal deaths plus emigration.
The epidemiological transition
The epidemiological transition model, proposed by Abdel Omran in 1971, explains why death rates change: the main causes of death shift from infectious diseases to chronic (degenerative) diseases. Infectious diseases spread from person to person or through water, food or insects, like cholera, tuberculosis and malaria. Chronic diseases develop over a long time and are tied to aging and lifestyle, like heart disease, cancer and diabetes.
- Stage 1, pestilence and famine: infectious disease, famine and violence cause most deaths. The Black Death of 1347–1351 is a classic example.
- Stage 2, receding pandemics: clean water, sewers and better nutrition cut infectious disease. This matches DTM Stage 2.
- Stage 3, degenerative and human-created diseases: people live long enough that heart disease and cancer become the leading killers.
- Stage 4, delayed degenerative diseases: medical care delays chronic disease deaths to older ages.
- Possible Stage 5, reemergence of infectious disease: antibiotic resistance, new viruses and global travel bring infections back, as COVID-19 showed. Omran described only the first three stages; other researchers added Stages 4 and 5 later.
Limits of the DTM
- It is based mostly on the history of Western Europe and North America, where change took about two centuries. Many countries today moved much faster.
- It can't predict when, or even whether, a country will move to the next stage.
- It assumes industrialization and urbanization drive falling birth rates. Policy, religion, culture and access to contraception also matter, and some countries' birth rates fell before they industrialized.
- It leaves out migration, which can reshape a population as much as births and deaths.
- Death rates fell quickly in many countries because medicine and vaccines were imported, so their Stage 2 growth was faster than Europe's ever was.
Worked examples
Try each one yourself first, then open the solution.
- Example 1
Explaining Stage 2 growth
Explain why population grows rapidly in Stage 2 of the demographic transition model.
Show the solutionHide the solution
- Step 1: State what changes: death rates fall sharply.
- Step 2: Give the cause: better food supplies, clean water, sanitation and vaccines mean fewer people die young.
- Step 3: State what doesn't change yet: birth rates stay high because cultural and economic reasons for large families remain.
- Step 4: Conclude: the widening gap between high births and low deaths produces a high rate of natural increase.
Answer: In Stage 2, death rates drop quickly because of better food, sanitation and medicine, but birth rates stay high, so the gap between births and deaths widens and the population grows rapidly.
Common mistakes
- Saying birth rates fall in Stage 2. Death rates fall first; birth rates fall in Stage 3.
- Treating the DTM as a prediction. It describes a past pattern and can't forecast timing.
- Mixing up the two models. The DTM tracks birth and death rates; the epidemiological transition tracks causes of death.
On the exam
- You may be given birth and death rate data or a pyramid and asked which stage a country is in; justify it with both rates.
- Free-response questions often ask for a limitation of the DTM. Give a specific one, like its basis in European history, rather than “it isn't always right.”
Connected topics
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Check yourself
4 questions on 2.5 The Demographic Transition Model. Pick an answer to see if you got it, and why.
In which stage of the demographic transition model does a population grow fastest, and why?
Which of the following is the strongest criticism of using the demographic transition model to predict the future of countries in Sub-Saharan Africa?
Japan's population has been falling since the late 2000s, with more deaths than births each year. Which stage of the demographic transition model does Japan best illustrate?
Which of the following best describes the change predicted by the epidemiological transition model as a country develops?
0 of 4 answered