2.5 The Demographic Transition Model

The Demographic Transition Model (DTM) is a five stage model that explains how a country's birth rates, death rates, and population growth change as it develops over time. The epidemiological transition is its partner model, explaining why death rates rise or fall in each stage by focusing on the main causes of death.

DTM AP Human Geography Definition

In AP Human Geography, the demographic transition model (DTM) explains population change over time by tracking crude birth rate, crude death rate, and rate of natural increase. The five stages show how death rates usually fall before birth rates, creating rapid growth in the middle stages and slower growth or decline in later stages.

Use the DTM to interpret population pyramids, compare countries, and explain how development, health care, urbanization, and family-size expectations shape population change.

more resources to help you study

practice multiple choiceFRQ practice & scoringcheatsheetsscore calculatorAMSCO guided noteskey terms

Why This Matters for the AP Human Geography Exam

This topic supports a core skill in AP Human Geography: explaining theories of population growth and decline. The DTM gives you a framework to read population change over time and connect it to a country's level of development. On the exam, you may be asked to describe spatial patterns in population data, match a country or population pyramid to a stage, or explain why birth and death rates shift between stages.

The DTM also links forward to later topics. You will use it again when you analyze population policies, aging populations, and economic development, so building fluency now pays off across multiple units.

Key Takeaways

• The DTM has five stages defined by the relationship between crude birth rate (CBR) and crude death rate (CDR), which together drive the rate of natural increase (RNI).
• Death rates usually fall first (Stage 2), then birth rates fall later (Stage 3), which is why population grows fastest in the middle stages.
• Each stage has a typical population pyramid shape, so you should be able to match a pyramid to a stage.
• The epidemiological transition explains the changing causes of death across stages, moving from infectious disease toward chronic and degenerative disease.
• Stage 5 (population decline) is a debated add-on to the original model, marked by very low birth rates and an aging population.
• The DTM is a model, not a law, so real countries do not always fit neatly into one stage.

The Demographic Transition Model

The Demographic Transition Model (DTM) uses five stages to explain how population changes over time as a society develops. The key to reading the model is watching two rates: the crude birth rate (CBR) and the crude death rate (CDR). The gap between them sets the rate of natural increase (RNI), which tells you whether a population is growing, stable, or shrinking.

You should be able to recognize each stage when you look at a population pyramid, since each stage produces a typical shape.

Stage 1: High Stationary

Stage 1 has a high birth rate and a high death rate. Because the two rates are roughly equal, the natural increase rate stays close to zero and the population stays about the same. This is sometimes called zero population growth.

No country is fully in Stage 1 today. For most of human history the entire world sat in this stage, which is why it took roughly 100,000 years for the global population to reach one billion. Small, isolated communities are sometimes described as being in Stage 1, but that is an illustrative example, not a fixed rule about any group.

Stage 2: Early Expanding

Stage 2 is where rapid population growth begins. The birth rate stays high, but the death rate drops sharply, so the rate of natural increase shoots up. Infant mortality is often still high, but people who survive tend to live longer. Longer life expectancy means three generations can overlap, so grandparents become more common.

On a population pyramid, Stage 2 has a very wide base that narrows quickly toward the top. Doubling time is short. As an example, several countries in Sub-Saharan Africa are often placed in Stage 2.

Stage 3: Late Expanding

In Stage 3 the birth rate falls while the death rate stays low. The population still grows, but more slowly than in Stage 2. As countries industrialize and urbanize, the total fertility rate (TFR) tends to drop, partly because more people work outside the home and family size shrinks.

The population pyramid for Stage 3 looks more like a pear, wider through the middle age groups. Countries often described as Stage 3 include Mexico, India, Colombia, and South Africa, as examples.

Stage 4: Low Stationary

Stage 4 has low birth rates and low death rates, so the rate of natural increase is close to zero again. Population is large but fairly stable. In some countries the population would shrink without net in-migration.

The Stage 4 pyramid is more even across age groups and looks closer to a column. Countries often placed in Stage 4 include the United States, China, Brazil, and Argentina, as examples.

Stage 5: Declining

Stage 5 is a debated add-on to the original model. Here birth rates stay very low while the population ages, so deaths can outpace births and the rate of natural increase turns negative. These countries have graying populations with fewer people in their childbearing years.

Some governments respond with pronatalist policies that try to encourage births. On a population pyramid, Stage 5 narrows at the bottom and can look top-heavy, almost like an upside-down pyramid. Countries often described as Stage 5 include Japan and several in Eastern Europe, as examples.

The Epidemiological Transition

The epidemiological transition explains the changing causes of death that drive the death rate in each DTM stage. While the DTM tracks the rates, the epidemiological transition tells you why people are dying.

• Stage 1: Most deaths come from infectious and parasitic diseases (such as plague and malaria) and from environmental causes like famine and natural disasters. Infant mortality is high.
• Stage 2: Death rates fall as nutrition, sanitation, and medicine improve. Fewer people die from infectious diseases as public health and infrastructure expand.
• Stage 3: People live much longer, and chronic, degenerative diseases tied to age, such as heart disease and cancer, become the leading causes of death.
• Stage 4: Better treatment and medical technology help more people survive chronic diseases, extending life expectancy further.
• Stage 5: Death rates can rise again mostly because the population is older. Some models suggest other factors may contribute, such as infectious diseases developing resistance to drugs, the spread of disease through poverty, and faster global transmission through increased travel and connection. Treat these proposed causes as debated rather than settled.

How to Use This on the AP Human Geography Exam

MCQ

Expect to match countries, data, or population pyramids to a DTM stage. A reliable approach is to check the birth rate and death rate first, then find the gap between them to estimate the rate of natural increase. A wide-based pyramid points to Stage 2, a pear shape suggests Stage 3, a column-like shape fits Stage 4, and a top-heavy shape points to Stage 5.

Free Response

If a prompt asks you to explain population change, use the DTM as your framework. Name the stage, describe what the birth and death rates are doing, and explain the result for the rate of natural increase. Connect the change to real drivers like industrialization, urbanization, improved health care, and the changing role of women in the workforce.

When a question involves causes of death or life expectancy, bring in the epidemiological transition to explain why death rates shift.

Common Trap

Do not assume every country fits perfectly into one stage. The DTM is a model that simplifies reality, so use it to explain trends, not to make exact predictions.

Common Misconceptions

• Birth and death rates do not fall at the same time. Death rates drop first (Stage 2), and birth rates lag behind (Stage 3). That delay is exactly what causes the population boom in the middle stages.
• Stage 1 is not the same as low population. Stage 1 means slow growth because high births and high deaths cancel out, not that few people exist.
• A high rate of natural increase does not mean a wealthy country. The fastest natural increase happens in Stage 2, which is usually associated with earlier stages of development, not the richest economies.
• Stage 5 is not officially fixed. The original model had four stages, and Stage 5 was added later to describe population decline, so its causes are still debated.
• The DTM is not a guaranteed path. Countries can move through stages at different speeds, and the model does not promise every country will follow the same route.
• The DTM and epidemiological transition are different models. One tracks birth and death rates and population change; the other explains the causes of death behind those rates.

zation, education, or population policy.

Related AP Human Geography Guides

• Unit 2 Overview: Population and Migration Patterns and Processes
• 2.2 Consequences of Population Distribution
• 2.1 Population & Migration
• 2.3 Population Composition
• 2.8 Women and Demographic Change
• 2.6 Malthusian Theory and Geography