One is a triumph: living longer than nearly anyone on the planet. The other is a warning: barely having children at all.

A South Korean born in 2024 can expect to live about 83.7 years. Yet South Korea’s total fertility rate was only 0.80 children per woman in 2025. That was up from 0.75 in 2024 and the record low of 0.72 in 2023, but it remained the world’s lowest fertility rate.

So what does it mean for a nation to be this long-lived and this reluctant to have children at the same time? The country is living out that collision in real time.

I am not a demographers, economist, or public-health researcher. What follows is reading and reflection on the data, not advice or prediction. Population projections are models, not certainties.

The longevity side of the ledger

The rise in life expectancy is easy to miss under all the alarm about fertility. In 1970, life expectancy was about 63.2 years. By 2024, it had risen by more than two decades to 83.7. The OECD identifies Korea as one of the member countries with the largest gains in life expectancy since 1970.

In the OECD’s latest comparable data, South Korean life expectancy was 83.5 years in 2023, 2.4 years above the OECD average. Decades of rising living standards, public-health improvements and wider access to medical care helped move the country from postwar poverty to the top tier for longevity within a single lifetime.

The fertility collapse

South Korea’s fertility rate was already low a decade ago, at 1.24 children per woman in 2015. It then fell for eight consecutive years, reaching 0.72 in 2023 before rising to 0.75 in 2024 and 0.80 in 2025. A rate of about 2.1 is usually described as the replacement level in a population with low mortality and no migration. South Korea remains far below it.

Experts point to a combination of pressures: costly education and difficulty combining careers with parenthood.

In 2024, 80 percent of elementary, middle and high-school students received private education, while spending reached 29.2 trillion won. Jennifer Sciubba of the Population Reference Bureau puts it bluntly: “education is prohibitively expensive, which disincentivizes having large families.”

OECD research argues that when gender-unequal norms and a large gender wage gap meet long and inflexible working practices, women can face a sharp conflict between employment and motherhood. Births outside marriage remain uncommon, so declining marriage has also meant fewer babies. The recent rise in marriages may help explain part of the fertility rebound, but two years of improvement do not reverse the long-term decline.

When a country lives long but barely replaces itself

In 2025, South Korea recorded 254.5 thousand births and 363.4 thousand deaths. The population shrank naturally for a sixth consecutive year.

When people live longer, the older end grows while the younger end thins out. Eventually the whole age structure changes.

Under the UN’s central scenario, South Korea’s population falls from roughly 52 million in 2026 to around 22 million by 2100, more than a halving. That scenario already assumes fertility recovers to about one child per woman by mid-century and 1.3 by 2100, while life expectancy rises to 91 years.

The worry is not just the headcount. By 2100, the projection has almost as many people of retirement age as of working age. Megan Huchko of Duke University puts the core anxiety plainly: “The concern with the prolonged very low fertility rate is the aging population, who may not have sufficient resources to care for them as the active labor force shrinks.” A smaller workforce supporting a larger retired population is a strain, not a guaranteed collapse.

Why this matters beyond South Korea

South Korea is the extreme case, but it may not be the exception. Costly cities, long hours, expensive schooling and uneven caregiving appear across much of the wealthy and fast-developing world. South Korea offers an early look at where the line bends if those forces persist.

The government has spent heavily on cash incentives and family support, yet fertility fell for most of that period. Sarah Barnes of the Wilson Center says research suggests “the impact is short lived and ultimately does not tend to increase the number of children a woman has, but may impact the timing of when she has a child or children.” Cash payments may change when people have children more than whether they have them at all.

Which leaves the question open. South Korea has done something notable at one end of life and something historically unusual at the other, and no one has a tidy answer for what happens when those trends run for another fifty years. The rest of the wealthy world gets to watch what a shrinking, aging, long-lived society looks like, perhaps before reaching its own version of the same arithmetic.