As fertility rates fall and longevity rises, the share of people aged 65 and over is climbing rapidly.

This visualization ranks the nations—having a population of at least one million—with the biggest senior populations today. It also shows how that lineup is set to change by 2100.

Data for this visualization is sourced from the UN World Population Prospects, which tracks and projects the share of adults aged 65+ in every country.

Ranked: Countries With the Most Seniors in 2025
In 2025, 22 of the 25 countries with the most seniors in 2025 are European.

Japan is one of three non-European nations in the top 25, and the country with the highest share of older adults (30% aged 65+).

Note: These estimates are made for territories with a population over one million. See this chart for a list without the population restriction.

Yet by 2050 and beyond, the projected gains in Europe’s older adult share taper, reflecting the mitigating effect of immigration.

East Asia’s Rapid Demographic Transition
While Hong Kong and Puerto Rico overtake Japan by mid-century, the most dramatic rise belongs to mainland China.

From outside the top 25 in 2025, China is expected to hold the world’s third-highest senior share by 2100 at nearly 46%.

Other East Asian countries like South Korea, Taiwan, and Singapore also surge, each pushing past the 40% threshold by century’s end.

Much like what’s happened in Europe, this aging sprint is driven by historically low fertility rates coupled with swift improvements in life expectancy.

Unlike Europe, immigration from younger countries, is (so far) not providing a moderating effect.

How Immigration is Helping Europe
Across Europe, inflows of migrants are already cushioning the region’s demographic squeeze.

Eurostat modeling shows that, without immigration, the EU’s population would shrink by up to one-third by 2100, versus just 6% in its baseline outlook.

In fact, recent gains in countries such as Spain and Germany have been almost entirely migration-driven. And the European Parliament warns that closing the gates would accelerate the rise in the old-age dependency ratio.

The OECD reaches the same conclusion. They say that expanding legal migration is one of the few realistic levers for slowing Europe’s march toward a 50% or higher retiree-to-worker ratio.

East Asia Contends With Migrants
Meanwhile, East Asia, remains one of the least-open regions to immigration.

Foreign-born residents make up barely 3% of Japan’s population and just over 5% of South Korea’s, with even lower shares in China and Taiwan.

Policy debate over large-scale immigration is limited, and cultural homogeneity is often prized.

Experts convened by Asia Society (linked above) note that, absent a turnaround, these low inflows leave East Asian societies locked into the steepest aging trajectories.

Yet those forecasts are not set in stone. In 2024 South Korea logged its first uptick in births in nine years. Deliveries rose 3.6% and fertility edged up to 0.75.

Thus, a meaningful change in sentiment around migration, or a sustained rebound in fertility, could easily reshape this 2100 outlook.

Source: visualcapitalist