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Unlock This CoursePopulations do not grow in a straight line. Over time, a country's birth rate and death rate change, and so does the size of its population. The demographic transition model (DTM) is a graph that shows this change in five stages, as a country becomes more developed. You already know how to work out natural increase from birth rate and death rate. The DTM shows how those two rates move over time.
Key terms:
| Stage | Birth rate | Death rate | Natural increase | Total population |
|---|---|---|---|---|
| 1 High stationary | High | High and fluctuating | Low or zero | Low and stable |
| 2 Early expanding | High | Falling fast | Very high | Rising rapidly |
| 3 Late expanding | Falling fast | Low, still falling slowly | High but falling | Still rising, but more slowly |
| 4 Low stationary | Low and fluctuating | Low and fluctuating | Low | High and stable |
| 5 Declining | Very low, below the death rate | Low, may rise a little as people age | Negative (natural decrease) | Falling |
A useful trick: the death rate falls first (stage 2), then the birth rate follows (stage 3). The gap between them is natural increase, so the gap is widest in stage 2 and the population grows fastest there.
Both rates are high. Families have many children because many die young, and children help on the farm. Death rates jump up in years of famine, disease or war, so they fluctuate. Births and deaths roughly cancel out, so the population stays small. Example: Britain before about 1760 is the usual textbook case. Today almost no whole country is in stage 1, though a few small isolated groups of people live in a similar way.
The death rate falls quickly because of more reliable food, clean water and sanitation, vaccines and medicines, and better healthcare. The birth rate stays high because people still want large families, infant mortality is only just starting to fall, contraception is hard to get and cultural or religious beliefs favour big families. Natural increase is very high. Example: Niger, where the fertility rate is about 6, is often given as a country still in this stage.
The birth rate falls fast. Reasons: better access to contraception and family planning; more girls in school and more women in paid work; people moving to cities, where children cost more and do not work the land; and fewer children dying, so parents need fewer births. Example: Egypt and Kenya are often placed here, as their birth rates have fallen but are still well above their death rates.
Both rates are low and bounce up and down a little, for example a small baby boom in good economic times. Families are small because children are expensive, many parents work and people marry later. The population is large but stable. Example: the USA and Australia are often placed here, as natural increase is low.
The birth rate falls below the death rate, so there is natural decrease. Many people live to old age, which keeps deaths up, and couples choose few or no children. The population falls unless migration fills the gap. Example: Japan is the classic case. Germany, Italy and South Korea are also often placed here.
Countries are placed in a stage by judging their rates against these patterns, and experts sometimes disagree. That is why textbooks word these examples with 'often'.
Fig. 1.1 shows made-up data for Country K.
| Year | Birth rate (per 1,000) | Death rate (per 1,000) |
|---|---|---|
| 1900 | 38 | 36 |
| 1930 | 37 | 25 |
| 1960 | 36 | 12 |
| 1990 | 24 | 8 |
| 2020 | 12 | 9 |
(a) Identify the stage of the demographic transition model that Country K had reached in 1960. [1 mark]
(b) Calculate the natural increase in Country K in 1960. [1 mark]
(c) Explain why the death rate in Country K fell between 1900 and 1960. [3 marks]
(d) Evaluate how useful the demographic transition model is for understanding population change. [6 marks]
(a) Stage 2 (1).
(b) 36 minus 12 = 24 per 1,000 (1).
(c) Better healthcare, medicines and vaccines meant fewer people died of disease (1). Cleaner water and sanitation reduced illnesses such as cholera (1). More reliable food supplies meant less hunger and famine (1).
(d) Level 3 answer: The model is useful because it is simple and shows clearly how birth and death rates change as a country develops. It is based on the real history of Britain, so it has evidence behind it. Country K fits the model well, as the death rate fell first and the birth rate followed, so the model can help governments predict that growth will slow and plan for schools and homes. However, it has limits. It was based on European experience, so poorer countries may not follow it in the same way or at the same speed. It also ignores migration, which can change a population a great deal, and stage 5 is debated. Overall, it is a useful starting point for understanding population change, but it should be used with care because real countries do not all follow the same path.
In an 'Evaluate' question on a model, give at least one strength and one limitation, link them to the data or a named country, and end with a clear judgement.