Population Demographics Explorer
Compare population pyramids across 30 countries spanning every region and stage of demographic transition. Project future populations with geometric and logistic growth models. All snapshot data comes from documented World Bank and UN figures.
Guided Experiment: Compare a young vs an old country pyramid
How do age-sex pyramids differ between countries at very different stages of demographic transition? What features would you predict for Nigeria's pyramid versus Japan's pyramid?
Write your hypothesis in the Lab Report panel, then click Next.
Nigeria
Africa, 223.8 million, growth 2.4%
Japan
Asia, 124.5 million, growth -0.5%
Controls
Demographic Comparison
Nigeria
- Region
- Africa
- Total population
- 223.8 million
- Annual growth
- 2.40%
- Fertility rate
- 5.10 per woman
- Life expectancy
- 53.6 years
- Median age
- 17.7 years
- Percent under 15
- 44.2%
- Percent 15 to 64
- 53.0%
- Percent over 65
- 2.8%
- Dependency ratio
- 88.5%
- Sex ratio
- 100.9 males per 100 females
Japan
- Region
- Asia
- Total population
- 124.5 million
- Annual growth
- -0.50%
- Fertility rate
- 1.30 per woman
- Life expectancy
- 84.1 years
- Median age
- 51.2 years
- Percent under 15
- 10.4%
- Percent 15 to 64
- 57.9%
- Percent over 65
- 31.7%
- Dependency ratio
- 72.8%
- Sex ratio
- 94.6 males per 100 females
Data Table
(0 rows)| # | Age Bin | Male % | Female % | Total % |
|---|
Reference Guide
Population Pyramid Shapes
Expansive (broad base). Wide bottom, narrow top. Indicates high fertility and short life expectancy. Examples include Nigeria, Ethiopia, Pakistan, Kenya.
Stationary (barrel). Roughly equal width across most age groups. Indicates fertility near replacement level and long life expectancy. Examples include the United States, United Kingdom, France, Australia.
Constrictive (inverted, top-heavy). Narrow base, wider middle and top. Indicates very low fertility and an aging population. Examples include Japan, Germany, Italy, South Korea.
Demographic Transition Theory
Stage 1. Pre-industrial. High birth rates and high death rates. Population grows slowly.
Stage 2. Death rates fall (better medicine, sanitation, food supply) while birth rates stay high. Rapid population growth.
Stage 3. Birth rates begin to fall (urbanization, education, contraception). Growth slows.
Stage 4. Birth rates near replacement (around 2.1 children per woman). Population stabilizes.
Stage 5. Below replacement fertility. Population begins to shrink and age. Japan, South Korea, Germany are here.
Growth Models
Geometric (compound). Population doubles repeatedly at a fixed rate.
Exponential. Continuous-time analogue. Equivalent to geometric for small r.
Logistic. Growth slows as population approaches a carrying capacity K. More realistic for long horizons.
Dependency Ratio
The dependency ratio captures how many non-working-age people each working-age person supports.
A high ratio can come from a young population (Nigeria) or an old one (Japan). Both stress economies but in different ways. Youth dependency demands schools and childcare. Old-age dependency demands pensions and healthcare.
Median Age vs Life Expectancy
Median age is the age that divides the population in half. Half are younger, half are older. It tracks how recently a country had high fertility.
Life expectancy at birth is the average age someone born today is expected to live to, given current age-specific death rates.
These two numbers are independent. South Korea has a median age near 45 and life expectancy near 84. Nigeria has a median age near 17 and life expectancy near 54. The Saudi Arabia pyramid has a male-skewed bulge in the 25 to 35 age range driven by migrant workers, not by birth or death rates.
Snapshot Data Note
All data shown is a static snapshot drawn from documented public sources. Total population figures are 2023 estimates. Age structures reflect each country's actual reported distribution rounded to 5-year bins. Historical population covers 1960 to 2020 in 5-year steps.
For live data and the full dataset across every country, year, and age band, consult data.worldbank.org and the UN World Population Prospects.
