Japan, China, South Korea: Inside East Asia’s Population Decline

By the populationclock.org team · Published August 17, 2026 · All figures: UN World Population Prospects 2024, medium variant

Three countries, one direction

Start with the raw numbers. Japan peaked in 2010 at about 128 million and holds around 123 million today; by 2100 the projection is 77.0 million. China peaked in 2021 at 1.43 billion and is projected to fall to 639 million by 2100, a loss of more than half a billion people in one country. South Korea peaked in 2021 and is projected to shrink from about 51.6 million today to 22.0 million by 2100, less than half its current size.

• Japan: peaked 2010, about 123 million in 2026, projected 77.0 million in 2100
• China: peaked 2021, about 1.41 billion in 2026, projected 639 million in 2100
• South Korea: peaked 2021, about 51.6 million in 2026, projected 22.0 million in 2100

The engine: fertility far below replacement

Keeping a population stable without immigration takes roughly 2.1 births per woman. In this dataset’s 2024 estimates, Japan stands at about 1.22, China at 1.01, and South Korea at 0.73, the lowest national rate in the world in this dataset. These are not blips; all three have been below replacement for decades. South Korea’s figure means each generation is roughly a third the size of the one before it.

Why so low? The honest answer is a stack of reasons that reinforce each other: intense work cultures and long hours, some of the world’s highest costs for housing and education, late marriage, and social expectations that still place most childcare on women. Governments in all three countries have spent years on subsidies and campaigns to raise birth rates, with little to show for it. Once small families become the norm, they tend to stay the norm.

Ageing is the sharper edge

Decline shows up in headcounts slowly, but in age structure fast. Japan’s median age is already about 49 and heading toward 53 by 2050. China, whose median age today is around 40, is projected to age past 52 by mid-century, meaning China will get old at a speed no large country has managed before. South Korea’s projected 2050 median age of 57 would make it one of the oldest societies on Earth.

The economic weight of that shift lands well before populations fall dramatically: fewer workers supporting more retirees, shrinking school cohorts, rural regions emptying ahead of cities. You can watch each population’s shape flip from a pyramid to an inverted top in the age charts on our country pages, for example Japan’s page, which animates the pyramid across today, 2050 and 2100.

Why this is hard to reverse

Demographic decline compounds just like growth does. When a generation of potential parents is small, even a recovery in birth rates produces few babies, which is why projections stay low for these three countries even under optimistic fertility assumptions. Immigration can offset decline, and Japan has quietly loosened its rules in recent years, but offsetting losses of this scale would require flows far beyond anything these societies have historically accepted.

None of this makes East Asia an outlier; it makes it the deep end of a global pool. Much of Europe has already passed its own peak too, though with fertility rates well above East Asia’s and more immigration cushioning the fall, and world population as a whole is projected to peak later this century, a story we cover in When will world population peak? What Japan, China and South Korea do about ageing, from robotics to pension reform to immigration, is effectively a rehearsal for everyone else.

Compare them yourself

The projections in this article are the UN World Population Prospects 2024 medium variant; our methodology page explains the processing. To see two of the trajectories on one chart, try the comparison tool: China vs Japan, or line up all three yourself on the compare page.