IB ESS HLTopic 8 — Human PopulationsPaper 1 & 2Case study~10 min read
Global Population Patterns
Population change is not happening at the same speed everywhere. Africa is young and growing fast; much of Europe and East Asia is old and starting to shrink. This page uses the demographic transition model to organise those differences, and gives you two case studies detailed enough to carry a long-answer question.
📚 What you need to know
Population patterns cover how people are spread across age groups and how size and structure change over time.
The DTM lets you place any country on a shared scale, so comparisons become straightforward.
Almost all of the world’s remaining population growth will come from countries in stages 2 and 3, mostly in sub-Saharan Africa and parts of South Asia.
Countries in stages 4 and 5 face ageing, shrinking workforces and rising old-age dependency.
Countries move through the stages at very different speeds. There is no fixed timetable.
You need two contrasting case studies with past, present and future for each.
The global picture on one line
No country is in stage 1 any more. Everywhere has clean water, vaccination and basic medicine in at least some form, so death rates have fallen everywhere. What separates countries now is how far their birth rates have fallen, and how long ago.
Placements are approximate and countries are large and varied inside their own borders. Use the model to organise an argument, not as a precise measurement.
Case study: Nigeria, stage 2 moving into stage 3
Past, roughly 30 or more years ago
Birth rates and death rates were both high. Infant mortality was high, and healthcare and sanitation were limited.
Access to education was poor, especially for girls.
Cultural and religious expectations supported large families, and children contributed to household income.
Present
Death rates have fallen sharply thanks to better healthcare, vaccination and sanitation.
Birth rates remain high, though access to education and family planning is rising, so the gap between births and deaths is wide and growth is rapid.
The population is extremely young: more than 40% are under 15, giving a very high youth dependency ratio.
Rapid urbanisation, with Lagos among the fastest growing cities in the world.
Future, next 30 years
Birth rates are expected to fall gradually as education and urbanisation spread, moving Nigeria into stage 3.
Strong population momentum means the total will keep rising for decades even as fertility falls.
The challenge is providing schools, healthcare, housing and above all jobs fast enough. If it succeeds, the large young population becomes a demographic dividend; if not, it becomes mass youth unemployment.
Case study: Japan, stage 4 moving into stage 5
Past, roughly 30 or more years ago
Rapid economic growth after 1945 raised incomes and living standards quickly.
Death rates fell to very low levels and life expectancy rose to among the highest in the world.
Birth rates fell steadily as the country urbanised, women entered the workforce, and the cost of raising children in cities rose.
Present
Fertility is roughly 1.3 children per woman, far below the replacement level of 2.1.
Nearly 30% of the population is aged 65 or over, giving a very high old-age dependency ratio.
The workforce is shrinking, the total population is falling, and rural areas in particular are emptying out.
Future, next 30 years
Decline is expected to continue, with negative population momentum keeping births low even if fertility rises.
Greater reliance on automation and robotics to cover labour shortages, and cautious increases in immigration.
The challenge is paying for pensions and healthcare from a shrinking tax base, and keeping rural services running.
Feature
Nigeria
Japan
DTM stage
2 moving to 3
4 moving to 5
Pyramid shape
Expansive, very wide base
Contracting, narrow base and broad top
Fertility
Well above replacement
About 1.3, far below replacement
Dependency burden
Youth dependency, over 40% under 15
Old-age dependency, nearly 30% over 65
Population trend
Growing rapidly
Falling slowly
Momentum
Strong positive momentum
Negative momentum
Main pressure
Jobs, schools, housing, urban services
Pensions, healthcare, labour shortages
Two case studies at opposite ends of the model will cover almost any question in this topic. Learn one number for each — over 40% under 15 for Nigeria, nearly 30% over 65 for Japan — and you have precise evidence for both.
Patterns worth being able to state
Growth is concentrated. Most of the world’s population increase this century is expected to come from a fairly small group of countries, mainly in sub-Saharan Africa.
Ageing is spreading. It began in Europe and Japan, but China, South Korea and much of Latin America are ageing faster than Europe ever did.
Fertility is falling almost everywhere. Even in countries with high fertility, the trend is downwards. The disagreement is about speed, not direction.
Cities are absorbing the growth. Most new population is being added to urban areas, which is why this topic runs straight into urban systems.
Migration reshapes the map. Some countries are ageing more slowly than their fertility alone would suggest, purely because working-age people keep arriving.
WORKED EXAMPLE
Compare the population structures of Nigeria and Japan, and explain how their positions on the DTM account for the difference.
Step 1: shape
Nigeria is expansive with a very wide base; Japan is contracting with a narrow base and a broad top.
Step 2: numbersNigeria: over 40% under 15. Japan: nearly 30% over 65.Step 3: link to the DTM
Nigeria is in stage 2, so deaths have fallen but births have not — a wide gap and a young population.
Japan is entering stage 5, so births have fallen below deaths and the population is ageing and shrinking.
Step 4: consequenceNigeria has high youth dependency; Japan has high old-age dependency.Same model, opposite ends, opposite problemsA comparison question needs both countries in every point. Never write a paragraph on one, then a paragraph on the other.
WORKED EXAMPLE
Evaluate the usefulness of the DTM for comparing countries such as Nigeria and Japan.
Step 1: strengths
It gives a shared scale, links birth and death rates to development, and predicts the shape of the pyramid you would expect.
Step 2: weaknesses
It was built on European history; it gives no timescale; it ignores migration, which matters a great deal for Japan; and it assumes countries only move forwards.
Step 3: judgement
Useful for organising a comparison, weak as a prediction.
A good framework, a poor forecastEvaluation questions want a verdict. Two strengths, two weaknesses, one clear conclusion.
💡 Exam tip
Structure every case study as past, present and future. That structure alone earns marks for development over time.
Carry one precise statistic per country. Vague answers about “a lot of young people” score poorly.
For comparisons, use linking words in every sentence: whereas, in contrast, compared with.
Say what a country’s structure means for spending. Schools or pensions is the quickest way to show understanding.
Build your own third and fourth case studies. Ethiopia and Germany, or Afghanistan and South Korea, work well.
If a question asks about global patterns, mention that growth is concentrated in a few regions while ageing is spreading in others.
⚠ Common mix-ups
Saying a country “is” a stage as though it were fixed. Countries are always moving, and large countries differ internally.
Assuming all of Africa is the same. North African fertility is far closer to Europe’s than to Niger’s.
Claiming Japan’s population falls because of a high death rate. Its death rate is low; it is high relative to a very low birth rate.
Confusing rapid growth with a large population. Nigeria grows quickly; China is far bigger but barely grows at all.
Writing two separate descriptions in a comparison question. Comparisons must be point by point.
Forgetting migration. Some ageing countries are stable in size only because of immigration.
Up next: Environmental Migration — what happens when the environment itself becomes the reason people move.
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