The big idea: A population pyramid shows a country's age and sex structure.
- Males are on the left, females on the right. - Age groups are stacked, youngest at the bottom. - Bar length = the share of people in that group.
Read the bars (values) and the overall shape — both are tested.
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
Key terms
- Age structure — how the population is split between young, working-age and old.
- Dependants — under-15s and over-65s, who rely on the working-age (15–64) population.
- Sex ratio — the balance of males to females (often per 100 females).
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
The shape tells the story. Compare the youthful pyramid above with this ageing one — the base is narrow and the top is wide.
Few children, many older people — a slow-growing, ageing population.
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
| Shape | What it means |
|---|---|
| Wide base, narrows quickly | Youthful — high birth rate, fast growth (often lower-income) |
| Narrow base, wide middle/top | Ageing — low birth rate, more elderly (often higher-income) |
| A bulge in one band | A past baby boom, or migration of working-age people |
| Longer female side at the top | Women tend to live longer — common in older age groups |
Stop wasting time on topics you know
Our AI identifies your weak areas and focuses your study time where it matters. No more overstudying easy topics.
Natural increase: The rate of natural increase is births minus deaths (per 1000 people per year), ignoring migration.
Positive → the population grows from within; negative → it shrinks.
Outline what is meant by the rate of natural increase.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Explain how migration can leave a place with an unbalanced ratio of males to females.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
How this is tested: A population pyramid (or a median-age line graph) is the figure you read most here. The low-mark commands stay close to the data: Identify the largest age group [1], State or Estimate a value off the axis [1], then Describe the shape [2]. Read the axis units first and always quote the figures you see.
Use this pyramid to answer the question below.
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
IB-style question — read the pyramid
Using the population pyramid above: (a) identify the age group with the most people [1]; (b) estimate the percentage aged 0–14 [1]; (c) describe the shape of the pyramid [2].
How to answer each part
- (a) Identify the largest group. Find the longest pair of bars — the 0–14 group has the longest bars, so it has the most people.
- (b) Estimate 0–14. Add the male and female bars for 0–14 (≈16% + ≈15%) → about 31%.
- (c) Describe the shape. It has a wide base that narrows quickly toward the top — a youthful population with a high birth rate.
Final answer
(a) the 0–14 group; (b) ≈ 31%; (c) wide base narrowing to a small top → youthful, high birth rate.
Data-response marks: Identify/State = read it straight off. Estimate = give a sensible figure from the axis. Describe = report the pattern (shape + figures), no reasons.