Picture a retired shipyard worker in Ulsan who has never once set foot in a gym. Demographers project he could still outlive almost every other man on the planet.

His genes are not the reason. A better explanation sits closer to home: the vegetables on his table, the clinic visit that costs him about the price of lunch, and a city built for walking.

In 2017, a team led by Majid Ezzati at Imperial College London, working with the World Health Organization, projected life expectancy in 35 industrialised countries out to 2030. Korean women took the headlines as the first national population forecast to average more than 90 years. Korean men were the quieter result: if the trends feeding the model held, they were projected to reach 84.1 years by 2030, edging out Switzerland and Australia for the top spot.

What the forecast actually claims

Mortality forecasting is brittle work, because every statistical model smuggles in its own assumptions about how death rates will behave decades from now. Instead of trusting one, Kontis, Ezzati and colleagues blended 21 of them into what they called a Bayesian model ensemble, weighting each model by how closely it had tracked real mortality history. The trick comes from weather forecasting, where disagreement between models becomes part of the output instead of something buried.

It comes down to one paper, one distribution of possible futures, and a central estimate rather than a promise.

The gene pool has not changed since 1970

How does a country add twenty years of life expectancy in two generations? Not through evolution. By 1970, the average newborn there could expect just over sixty years, well behind most of Western Europe, according to the historical series compiled by Our World in Data. By 2024, the national life table put it at 83.7 years, with men at 80.8 and women at 86.6. Korean men now run 2.3 years ahead of the OECD male average. No population edits its DNA that fast, which leaves food, medicine, work and the shape of the street to explain the gap.

Getting rich without getting heavy

Most countries that industrialised quickly grew fat on the way through. Korea largely did not. OECD figures reported by The Korea Herald put adult obesity at around 5 per cent, second lowest in the club behind Japan, at a point when the United States was above 38 per cent.

Some of that is arithmetic rather than virtue, since the OECD threshold is a body mass index above 30 and Korea’s domestic definition starts at 25, which pushes the local figure into the thirties. Even so, severe obesity stayed rare while incomes multiplied, and the everyday Korean table held its shape: rice, soup, fish, fermented vegetables, small portions of meat. Blood pressure stayed low too, and deaths from heart disease and stroke fell as the diet held.

Insurance that arrived in twelve years

A worker at a firm with five hundred employees or more got covered first, in 1977. Everyone else had to wait. By 1989, coverage reached the entire country, an expansion documented in the American Journal of Public Health as a twelve-year sprint to universal coverage that most Western analysts had expected to collapse under its own costs. Separate insurance societies were folded into a single payer in 2000.

Cheap, frequent contact with a doctor is unglamorous and enormously powerful. It is how a rising cancer marker or a blood pressure reading gets caught in a man who still feels fine. Cancer remains Korea’s leading cause of death all the same, with a lifetime mortality risk close to one in five, a reminder that screening finds disease early without curing it.

The exercise nobody logs as exercise

Then there is walking, the intervention no health ministry has to fund. When Stanford researchers analysed 68 million days of smartphone step data across 111 countries for a paper in Nature, the global average came out to roughly 5,000 steps a day. The sharper finding sat underneath that number: the gap between a country’s most and least active people predicted obesity better than average activity did, a pattern the researchers called activity inequality. South Korea sat among the handful of countries with the smallest such gap, alongside Japan, Sweden and Hong Kong. Most people there walked a broadly similar amount, and no small fit minority was propping up the national number on its own.

It is a fair bet that dense, walkable cities like Seoul have something to do with that evenness. Subways, stairs and short blocks hand nearly everyone the same baseline dose of movement, whether they think of it as exercise or not.

Which is exactly the part now under threat.

Analysis of the Korean National Health and Nutrition Examination Survey found that adherence to recommended leisure-time exercise slid from 25.5 per cent in 2014 to 20.5 per cent by 2021. Over the same seven years, the share of adults sitting for eight hours or more a day climbed from 46.7 per cent to 63 per cent. Mortality data take years to catch up with a shift like that, which is why the 2030 estimate has not yet had to reckon with it.

The 84.1-year projection rests on men who were rebuilt by a country that made them walk, fed them vegetables and put a clinic on every second corner. Their sons order delivery, drive to work and take the lift. Whether the forecast holds will say less about Korean biology than about how long a habit survives once the city stops enforcing it.