How and why do populations change, and what does the demographic transition model reveal?
Natural population change; the demographic transition model and its stages; population structure and population pyramids; and migration and its causes and consequences for source and destination areas.
A focused answer to the AQA A-Level Geography 3.2.4 content on population change, covering natural change, the demographic transition model and its stages, population structure and pyramids, and migration and its causes and consequences for source and destination areas.
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What this dot point is asking
AQA section 3.2.4 wants you to explain natural population change, the demographic transition model (DTM) and its stages, population structure and pyramids, and migration, its causes and its consequences for source and destination areas. It is the demographic core of the population topic.
Natural population change
Birth and death rates are driven by development: sanitation, nutrition, medicine, female education, urbanisation and access to contraception. Total population change adds net migration to natural change.
The demographic transition model
The DTM generalises how birth and death rates change as a country develops:
- Stage 1 (high fluctuating): high birth and death rates, low and unstable growth.
- Stage 2 (early expanding): death rates fall (sanitation, food, medicine), birth rates stay high, so rapid growth.
- Stage 3 (late expanding): birth rates fall (contraception, education, urbanisation, lower infant mortality), so growth slows.
- Stage 4 (low fluctuating): low birth and death rates, low stable growth.
- Stage 5 (sometimes added): death rates slightly exceed birth rates, giving a shrinking, ageing population.
The DTM is a useful generalisation, but not every country follows it exactly, and the timing varies.
Population structure and pyramids
Migration and its consequences
Migration is movement of people, internal (within a country, such as rural-urban) or international. It is driven by push factors (poverty, conflict, lack of opportunity, environmental stress) and pull factors (jobs, safety, services, family). Its consequences are mixed:
- Source areas: gain remittances and reduced unemployment, but suffer brain drain (loss of skilled, working-age people) and a distorted age structure.
- Destination areas: gain labour, skills, a younger workforce and cultural diversity, but face pressure on housing and services and possible social tension.
The balance depends on the type, scale and management of the migration.
Try this
Q1. Define natural change. [2 marks]
- Cue. The difference between birth and death rates (births minus deaths per 1,000 per year), excluding migration.
Q2. Describe what happens to birth and death rates in Stage 2 of the DTM. [2 marks]
- Cue. Death rates fall sharply (sanitation, food, medicine) while birth rates remain high, giving rapid growth.
Q3. Explain one consequence of international migration for a source area. [3 marks]
- Cue. Brain drain: the loss of skilled, working-age people weakens the source economy and distorts its age structure (though remittances are a benefit).
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 2019 (style)6 marksExplain how the demographic transition model accounts for changing population growth.Show worked answer →
A 6 mark "explain" question (AO1). The demographic transition model (DTM) shows how birth and death rates, and so natural change, alter as a country develops.
Stage 1: high, fluctuating birth and death rates, so low growth. Stage 2: death rates fall (better sanitation, food, medicine) while birth rates stay high, so growth is rapid. Stage 3: birth rates fall (contraception, education, urbanisation, lower infant mortality), so growth slows. Stage 4: low birth and death rates, so growth is low and stable. A Stage 5 is sometimes added, with death rates above birth rates and a shrinking, ageing population.
Markers reward explaining the changing gap between birth and death rates at each stage and the development reasons behind the changes. Top answers note the model is a generalisation that not all countries follow exactly.
AQA 2021 (style)9 marksAssess the consequences of international migration for source and destination areas.Show worked answer →
A 9 mark "assess" question (AO1 plus AO2): reach a judgement. For destination areas: gains include filling labour shortages, a younger workforce, skills and cultural diversity; costs include pressure on housing and services and possible social tension. For source areas: gains include remittances and reduced unemployment; costs include brain drain (loss of skilled workers) and a distorted population structure (loss of young adults).
The judgement: consequences are mixed and context-dependent, generally positive economically for destinations and through remittances for sources, but with social costs and the brain-drain problem for sources; the balance depends on the type and scale of migration and the policies in place. Reward a calibrated conclusion that weighs economic against social consequences for both areas, with examples.
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Sources & how we know this
- AQA A-level Geography (7037) specification — AQA (2016)