Epidemiological Transition Model in AP Human Geography

The ETM explains death rates, and the DTM tracks everything else

The two models get treated as one, but they answer different questions. The Demographic Transition Model (DTM) tracks birth rates, death rates, and total population growth across stages of development. The ETM looks only at mortality and asks what's killing people at each stage.

That's how the course frames it. In Unit 2 (Population and Migration), Topic 2.5: The Demographic Transition Model asks you to explain the theories behind population growth and decline over time. The DTM is the tool for how populations change, and the epidemiological transition is the tool for why death rates change.

A quick test works on most question stems. If the question is about causes of death (plague versus heart disease), it's the ETM. If it's about birth rates, natural increase, or the overall growth curve, it's the DTM.

Omran's stages compared with the DTM

The ETM stages can be compared with DTM stages, but the two models describe different aspects of population change. The fourth stage was added by later researchers, and the fifth is still debated.

• Stage 1: Pestilence and famine. Infectious and parasitic diseases, plague, and food shortages keep death rates high and unstable. The Black Death in 14th-century Europe is the classic example. Compares to DTM Stage 1.
• Stage 2: Receding pandemics. Better sanitation, clean water, and food supply cut deaths from diseases like cholera, so death rates drop fast. John Snow's 1854 tracing of a London cholera outbreak to a contaminated water pump shows how public health knowledge pushed this along. Compares to DTM Stage 2, when population grows rapidly.
• Stage 3: Degenerative and human-created diseases. People live long enough that heart disease, cancer, and stroke become the main killers. Compares to DTM Stage 3 moving into Stage 4.
• Stage 4: Delayed degenerative diseases. Chronic diseases are still the main killers, but medicine delays them, so people live with heart disease or cancer for years. Compares to DTM Stage 4.
• Possible Stage 5: Reemergence of infectious diseases. Antibiotic resistance, global travel, and poverty bring infectious disease back as a threat, even in wealthy countries.

Watch the numbers. DTM Stage 5 is about population decline from very low birth rates, while ETM Stage 5 is about returning infectious disease. A question about a shrinking, aging population belongs to the DTM.

What moves a country from cholera deaths to heart disease

The ETM is a model about causes, so the exam wants the factors behind each shift, and they line up with Topic 2.4: Population Dynamics. Mortality is one of the three forces (with fertility and migration) that decide whether a population grows or shrinks, and the course says those rates are shaped by social, cultural, political, and economic factors.

For the early drop in deaths, name specific changes like sewers and clean water, vaccines and antibiotics, better crop yields, and public health campaigns. For the later shift to chronic disease, the drivers are longer life expectancy, an aging population, and lifestyle changes like processed diets, less physical activity, and smoking.

Topic 2.2: Consequences of Population Distribution connects here too, since population density shapes how services like medical care get delivered. A rural area far from hospitals can show earlier-stage patterns of preventable deaths even inside a country that's mostly in Stage 4. That's a scale argument, and it can strengthen a free-response answer.

Matching a cause-of-death description to a model and stage

Say a stem describes infectious disease deaths falling while heart disease and cancer are rising. That shift toward chronic causes of death suggests ETM Stage 3. If the stem also shows people living longer with those diseases, so deaths from them come later in life, that could support ETM Stage 4.

Assigning a DTM stage takes more than causes of death. You need information about birth and death rates before you can place the country on the DTM. Stimulus versions might give a chart of leading causes of death in two countries.

On the free response, the ETM fits Question 2 (One-stimulus question) or Question 3 (Two-stimuli question) when the stimulus is mortality data, a population pyramid, or a comparison of death rates. A strong answer names the stage, names its dominant cause of death, and explains a specific development factor behind the shift, such as clean water lowering cholera deaths. The ETM also connects naturally to economic development.

One common mistake involves the crude death rate. Many assume it keeps falling in Stage 4, but in aging countries it can rise because so many people are elderly, even with high life expectancy. Japan's crude death rate now exceeds its crude birth rate. A rising death rate there signals an aging population, not worse health care.