3 Types of Population Pyramids: Expansive, Constrictive and Stationary
Updated October 6, 2026
A population pyramid plots a country’s people by age and sex. Its outline falls into one of three broad shapes, and that shape is a quick read on how births have changed over past decades.
Population pyramids come in three types: expansive (a wide base), stationary (similar numbers in each age group), and constrictive (a narrow base). The width of the base reflects how a country’s birth rate has changed over recent decades. The type is read from the age structure alone, so it overlaps with a country’s demographic-transition stage but does not match it one-to-one.
Expansive pyramids: a wide base
An expansive pyramid has a broad base that narrows steeply with age — many children, fewer older people. In the rule, under-15s make up at least 30% of the population. 68 countries have an expansive pyramid in 2026; all are early in the transition — 26 in Stage 2 and 42 in Stage 3.
- Population
- 28,814,879
- Births /1,000
- 40.2
- Deaths /1,000
- 8.4
- Natural change /1,000
- +31.8
- Children per woman
- 5.64
- Median age
- 15.7
- Under 15
- 45.8%
- 65 and older
- 2.6%
Stationary pyramids: a straight-sided middle
A stationary pyramid has roughly straight sides — similar numbers in each age group up to old age. In the rule, that is the in-between case: under-15s between 20% and 30% of the population, or below 20% with a base that has not yet pulled in. 48 countries have a stationary pyramid in 2026, spread across the middle of the transition: 22 in Stage 3, 24 in Stage 4 and 2 in Stage 5.
- Population
- 1,476,625,577
- Births /1,000
- 15.6
- Deaths /1,000
- 6.7
- Natural change /1,000
- +8.9
- Children per woman
- 1.93
- Median age
- 29.2
- Under 15
- 23.8%
- 65 and older
- 7.6%
Constrictive pyramids: a narrow base
A constrictive pyramid is narrower at the base than in the middle — fewer children than parents and grandparents. In the rule, under-15s are below 20% and the youngest band has pulled in below the working-age cohorts, which means births have fallen well below past levels. 78 countries have a constrictive pyramid in 2026. A narrow base does not by itself mean decline: of those 78, 39 are in Stage 5 (deaths outnumber births) and 39 are in Stage 4 and still growing, including the United States.
The United States has a constrictive pyramid, yet its 10.5 births per 1,000 still exceed its 9.0 deaths, so its population keeps growing. Japan has a similar shape but the opposite balance — 6.1 births against 12.8 deaths — so its population is falling. Same outline, different direction.
- Population
- 122,427,731
- Births /1,000
- 6.1
- Deaths /1,000
- 12.8
- Natural change /1,000
- −6.7
- Children per woman
- 1.23
- Median age
- 50.2
- Under 15
- 11.0%
- 65 and older
- 30.2%
How the three shapes line up with the stages
The shape tracks a country’s birth history, which overlaps with the demographic-transition stage without being the same thing. Expansive pyramids are all in Stage 2 (26) or Stage 3 (42). Stationary pyramids straddle Stage 3 (22), Stage 4 (24) and Stage 5 (2). Constrictive pyramids split between Stage 4 (39) and Stage 5 (39). For the rates behind each stage, see the five stages of the demographic transition.
The stage rule, which is separate from the pyramid-type rule above:
We place each country by its 2026 UN projections: Stage 5 if deaths exceed births; otherwise Stage 4 if women have fewer than 2.1 children on average; otherwise Stage 2 if there are at least 30 births per 1,000 people; otherwise Stage 3. No country meets the conditions of Stage 1 today.
Frequently asked questions
What are the three types of population pyramids?
Expansive: a wide base — under-15s are at least 30% of the population. Stationary: roughly straight sides — similar numbers in each age group. Constrictive: a narrow base — under-15s below 20% — showing that births have fallen well below past levels; such a country may still be growing or may be shrinking.
Which countries have expansive pyramids?
68 countries in 2026. All are early in the transition: 26 in Stage 2 and 42 in Stage 3. Niger is a clear example, with 40.2 births per 1,000 and 5.64 children per woman.
What does a constrictive pyramid mean?
A narrow base: births have fallen well below past levels. 78 countries have one in 2026. It does not by itself mean decline — 39 are still growing (the United States, 10.5 births versus 9.0 deaths per 1,000) and 39 are shrinking (Japan, 6.1 versus 12.8).
How does pyramid type relate to the demographic transition?
Loosely — the type reflects birth history, so it overlaps with the stage without matching it. Expansive pyramids are all Stage 2 or 3; stationary pyramids span Stages 3 to 5; and constrictive pyramids split between Stage 4 (39) and Stage 5 (39), which is why a constrictive pyramid can belong to a growing country like the United States.
Sources
- United Nations, Department of Economic and Social Affairs, Population Division (2024), World Population Prospects 2024, https://population.un.org/wpp/.