How and why do birth and death rates change as a country develops, and what model captures that path?
Topic 2.5 The Demographic Transition Model: explain the stages of the Demographic Transition Model and the Epidemiological Transition, and evaluate the model's usefulness and limits.
A focused answer to AP Human Geography Topic 2.5, explaining the five stages of the Demographic Transition Model, the matching Epidemiological Transition, the population pyramids and growth rates at each stage, and the strengths and limits of the model.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this topic is asking
Topic 2.5 introduces the Demographic Transition Model (DTM), the central framework of the whole unit. The College Board wants you to explain how birth and death rates, and therefore population growth, change as a society develops through a sequence of stages, to connect each stage to a population pyramid and a level of development, and to pair it with the Epidemiological Transition (how the leading causes of death change). Crucially, the exam also wants you to evaluate the model: it is a useful generalization, not a law, and you must know its limits.
The stages of the DTM
The model tracks crude birth rate, crude death rate, and the rate of natural increase through stages of development.
Each stage matches a characteristic population pyramid (Topic 2.3): Stage 2 has a wide base, Stage 4 a column, and Stage 5 a narrow base with a heavy top. The fastest growth and highest natural increase always occur in Stage 2, where death rates have dropped but birth rates have not yet followed.
The Epidemiological Transition
The CED pairs the DTM with a model of how people die.
The two transitions move together: falling death rates in DTM Stage 2 come largely from conquering infectious disease, the heart of the epidemiological transition.
Why birth and death rates change
The model is driven by development:
- Death rates fall first (Stage 2) thanks to clean water, sanitation, vaccination, antibiotics, and reliable food. This is often imported technology, so it can happen quickly.
- Birth rates fall later (Stage 3) as societies urbanize, women gain education and employment, contraception spreads, and child survival rises so families choose fewer children. Cultural change is slower than medical change, which is why births lag deaths and Stage 2 growth is so rapid.
The limits of the model
The exam explicitly wants you to evaluate the DTM, not just recite it.
Why this matters for the exam
The DTM ties together fertility, mortality, population pyramids, and aging, and it is one of the most heavily tested frameworks on the exam. FRQs ask you to describe a stage, explain why rates change, match a country or pyramid to a stage, and critique the model's assumptions, so prepare to do all four.
Try this
Q1. Identify the DTM stage with the highest rate of natural increase, and explain why. [Recall]
- Cue. Stage 2; death rates have fallen sharply while birth rates remain high, producing the widest gap between them and the fastest growth.
Q2. Explain one limitation of using the Demographic Transition Model to predict a developing country's future population. [Short explanation]
- Cue. The model is based on Western Europe and ignores migration, government policy, and shocks like war or disease, so a country may not follow the same path or timing.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AP 2019 (style)1 marksIn which stage of the Demographic Transition Model is the rate of natural increase highest? (A) Stage 1. (B) Stage 2. (C) Stage 4. (D) Stage 5.Show worked answer →
A stimulus-style multiple choice item. The correct answer is (B).
In Stage 2, death rates fall sharply due to better healthcare and sanitation while birth rates remain high, producing the widest gap between them and therefore the highest rate of natural increase and fastest population growth. Stage 1 (A) has high but balanced rates; Stage 4 (C) has low balanced rates; Stage 5 (D) may have natural decrease.
The exam reward is knowing that the largest birth-death gap, and thus the fastest growth, occurs in Stage 2.
AP 2021 (style)3 marksThe Demographic Transition Model describes how populations change as societies develop. (A) Describe what happens to birth and death rates in Stage 3 of the model. (B) Explain ONE reason death rates fall during Stage 2. (C) Explain ONE limitation of the Demographic Transition Model as a tool for predicting a country's future.Show worked answer →
A 3-point describe-explain FRQ.
(A) Describe (1 point): in Stage 3 the death rate stays low while the birth rate falls significantly, so the rate of natural increase slows and population growth begins to moderate.
(B) Explain (1 point): death rates fall in Stage 2 because of improvements such as better healthcare and medicine, clean water and sanitation, and more reliable food supply, which reduce deaths from disease and famine.
(C) Explain (1 point): the model is based on the experience of Western Europe, so it may not predict the path of every country; it does not account for migration, government policy, war, or disease, and the timing and pace of transition vary, so it is a generalization rather than a precise forecast.
Markers reward an accurate description of the stage and a clear reason and limitation.
Related dot points
- Topic 2.4 Population Dynamics: define and calculate the rates of fertility, mortality, and natural increase, and explain the factors that drive them.
A focused answer to AP Human Geography Topic 2.4, covering the crude birth and death rates, total fertility rate, infant mortality rate, the rate of natural increase, doubling time, and the social and economic factors that drive fertility and mortality.
- Topic 2.3 Population Composition: use age, sex, and dependency structure, read population pyramids, and explain what composition reveals about a society.
A focused answer to AP Human Geography Topic 2.3, covering age and sex structure, the sex ratio, the dependency ratio, how to read and interpret population pyramids, and what a population's composition reveals about its stage of development and future.
- Topic 2.6 Malthusian Theory: explain Thomas Malthus's argument about population and resources, evaluate it against historical evidence, and contrast it with neo-Malthusian and critical responses.
A focused answer to AP Human Geography Topic 2.6, explaining Malthus's claim that population grows faster than food supply, the checks he predicted, why his forecast has so far failed, and the neo-Malthusian and critical (Boserup) responses.
- Topic 2.9 Aging Populations: explain the causes of population aging and the economic, social, and political challenges and responses it brings.
A focused answer to AP Human Geography Topic 2.9, explaining why populations age, the rising old-age dependency ratio, the economic and social challenges of an aging society, and the policy responses including immigration and pronatalism.
- Topic 2.8 Women and Demographic Change: explain how women's changing social, economic, and political status influences fertility rates and population growth.
A focused answer to AP Human Geography Topic 2.8, explaining how women's education, employment, access to family planning, and political and economic status drive declining fertility, and how these changes connect to the demographic transition.
Sources & how we know this
- AP Human Geography Course and Exam Description — College Board (2020)