Two children born on the same day, one in Niger and one in Japan, enter completely different worlds.
One is surrounded by other children in a nation where half the population is barely a teenager.
The other is one of the youngest people in a country where the typical resident is closing on 50.
That contrast, the divide between young nations and old nations, is one of the defining features of the world’s population.
The gap is not small. At the extremes, the typical resident of the youngest countries is more than three decades younger than that of the oldest.
TL;DR
- Africa is the youngest region by far, with 21 countries reporting a median age below 20, led by Niger at 15, Uganda at 16 and Mali at 16, together home to 790 million people.
- At the other end, Europe and East Asia hold the oldest populations, including Monaco at 57, Japan at 50, Italy at 48 and Germany at 47.
- The split is driven by two forces working in opposite directions: high fertility and improving child survival keep African populations young, while decades of low birth rates and long life expectancy age Europe and East Asia.
The data below are from the UN Population Division and Our World in Data.
| wdt_ID | wdt_created_by | wdt_created_at | wdt_last_edited_by | wdt_last_edited_at | End of the spectrum | Example countries | Median age (approx.) | Core driver |
|---|---|---|---|---|---|---|---|---|
| 1 | emmanuel-ashemiriogwa | 18/08/2026 09:42 AM | emmanuel-ashemiriogwa | 18/08/2026 09:42 AM | Youngest | Niger, Central African Republic, Somalia, Mali, Chad | 15 to 16 | High fertility, falling child mortality |
| 2 | emmanuel-ashemiriogwa | 18/08/2026 09:42 AM | emmanuel-ashemiriogwa | 18/08/2026 09:42 AM | Older middle | United States, United Kingdom, Canada | 38 to 41 | Below-replacement fertility, buffered by migration |
| 3 | emmanuel-ashemiriogwa | 18/08/2026 09:42 AM | emmanuel-ashemiriogwa | 18/08/2026 09:42 AM | Oldest | Monaco, Japan, Italy, Germany, South Korea | 46 to 57 | Low fertility plus long life expectancy |
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Why some nations stay young
Youth is a product of high birth rates meeting improving survival.
In the Central African Republic, the world’s lowest median age, around 15, means that half the population has not yet reached 16, with 49 percent under 15.
When families are large, and more children survive to adulthood, each generation dwarfs the one before, and the median age stays low.
These “youth bulge” nations hold enormous potential if they can build enough schools and jobs, and serious strain if they cannot.
Why some nations grow old
Aging is the mirror image: fewer births each year combined with people living longer.
Europe and East Asia have had below-replacement fertility for decades, so the base of their population pyramids has narrowed while the top has thickened.
The result is shrinking workforces and mounting pressure on pensions and healthcare, the challenges that define policy in Japan, Italy and South Korea today.
ALSO READ: Where the World Is Youngest — Share of Population Under 15 by Country
ELI5
In some countries, like Niger, most people are kids and teenagers.
In others, like Japan, most people are middle-aged or older.
This happens because places with lots of babies stay young, and places with few babies and long lives grow old. Each situation brings its own big challenges.
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