What Is a Population Pyramid?
A population pyramid is a back-to-back bar chart showing how many people of each age and sex live in a country. Males are shown on the left, females on the right, with the youngest age group at the bottom and the oldest at the top.
- Base (bottom bars): the youngest age groups. A wide base means a high birth rate.
- Sides: how quickly each cohort shrinks as it ages — steep, fast-narrowing sides usually mean a higher death rate at younger ages.
- Top (highest bars): the oldest age groups. A wide top means a large elderly population.
- Left vs. right: male population (left) vs. female population (right) — usually similar, but watch for skews.
- Bulges and notches: unusually large or small cohorts, often caused by wars, baby booms, migration waves, or government policy.
The Three Classic Shapes
Most population pyramids fall into one of three general shapes, each linked to a different stage of the Demographic Transition Model.
Expansive
A wide base that narrows quickly toward the top. High birth rate, high natural increase, and a very young population. This shape suggests rapid future population growth.
Stationary
Roughly column-shaped, with similar numbers of people in most age groups. Birth and death rates are both low and close to balanced — slow or minimal future growth.
Constrictive
Narrower at the base than in the middle or top. Birth rate has fallen below the level needed to replace the population — the population is likely to shrink over time.
Two Real Exceptions
Not every country fits neatly into one of the three shapes above. These two are worth knowing well.
Qatar — Migration-Distorted
Qatar's pyramid is dominated by a huge spike of working-age men — the result of a massive temporary migrant labor force, not natural births and deaths. This is the same limitation of the Demographic Transition Model you may have seen elsewhere: the classic model only tracks natural change, not migration.
China — Policy-Shaped
China's relatively small youngest cohorts compared to its large 40–49 cohort reflect decades of government fertility policy (including the one-child policy), not a gradual, "natural" demographic transition.
The Demographic Transition Model, Stage by Stage
Each pyramid shape above corresponds to a stage of the Demographic Transition Model. These are generalized patterns based on historical observation, not fixed numerical boundaries — countries can show mixed or borderline characteristics, as Qatar and China show above.
| Stage | Birth Rate | Death Rate | Natural Change | Typical Pyramid Shape |
|---|---|---|---|---|
| 1 | High Stationary High and fluctuating (roughly 35–50 per 1,000). Limited access to reliable food supplies, sanitation, healthcare, and disease control contributes to high mortality. |
High and fluctuating (roughly 35–50 per 1,000) | Little long-term change — population rises and falls with famine, disease, and conflict | Short and wide at the base, narrowing quickly — historic; almost no countries remain here today |
| 2 | Early Expanding Remains high (roughly 35–50 per 1,000) |
Falls rapidly as food security, clean water, and basic healthcare improve (roughly 10–20 per 1,000) | Rises sharply — typically the fastest period of population growth | Expansive — very wide base, rapid taper (e.g. Niger) |
| 3 | Late Expanding Begins falling as education, urbanization, and family planning access spread (roughly 15–30 per 1,000) |
Continues falling, but more slowly (roughly 5–10 per 1,000) | Still positive, but growth begins to slow | Between Expansive and Stationary — narrower base, fuller middle (e.g. Bangladesh) |
| 4 | Low Stationary Low and relatively stable (roughly 9–15 per 1,000) |
Low and relatively stable (roughly 8–12 per 1,000) | Close to zero — further growth, where it occurs, often comes from migration | Stationary — roughly column-shaped (e.g. United States) |
| 5 | Declining Very low (roughly 7–10 per 1,000) |
Can rise as the population ages (roughly 10–13+ per 1,000) | Negative — deaths outnumber births, producing natural decrease | Constrictive — narrower base than middle or top (e.g. Japan) |
Key Vocabulary
Test Yourself — 20 Questions
Click an answer for instant feedback. Every question has exactly one correct answer.
Submit to Your Teacher
Sends your quiz score and answer breakdown to your teacher.