In February 2017, an international team led by Majid Ezzati, professor of global environmental health at Imperial College London, published a paper in The Lancet projecting future life expectancy across 35 industrialised countries. The study, conducted in collaboration with the World Health Organization, used a novel statistical method called Bayesian model ensemble — combining the outputs of 21 separate forecasting models — to produce more robust projections than any single model could deliver. The result, which received substantial international press coverage, was that women born in South Korea in 2030 would have an average life expectancy of approximately 90.8 years, making them the first national population in recorded human history projected to cross the 90-year threshold on average.
The number is not certain. According to the Lancet paper itself, the model assigned a 57 percent probability that average female life expectancy in South Korea would exceed 90 years by 2030, and a 90 percent probability that it would exceed 86.7 years — the figure that, in 2012, was the highest national female life expectancy ever recorded anywhere in the world. The 90-year barrier is therefore more likely than not but not guaranteed in the projection. What is much more confidently predicted is that South Korea will be the first country to seriously test the threshold, with projected female life expectancy substantially exceeding that of every other country in the study, including the historical longevity leader Japan, projected at 88.4 years, and France, projected at 88.6 years.
Why South Korea
The drivers of South Korea’s exceptional longevity gains over the past several decades are not exotic. They are a relatively familiar combination of broad-based socioeconomic improvement, healthcare access, and population health behaviours, applied with unusual consistency and equity across the country’s population. According to the EurekAlert press release accompanying the Lancet study, the key factors identified by the research team include improvements in childhood nutrition; widespread access to healthcare through the country’s National Health Insurance Service, which has covered essentially the entire population since the late 1980s; relatively low rates of obesity by international standards, with average body mass indexes well below those of comparable industrialised countries; lower average blood pressure than Western peers; and broadly equitable distribution of these improvements across socioeconomic classes.
The equity factor is what most distinguishes South Korea from the United States in the same projections. Both countries are wealthy industrialised democracies with sophisticated medical systems. The United States, however, is projected to fall significantly behind by 2030 — to 83.3 years for women and 79.5 years for men, near the bottom of the 35-country list. Ezzati and colleagues identified obesity, high maternal and infant mortality rates, unequal access to healthcare, and high homicide rates as the main factors holding the US back. The contrast is that South Korea has distributed its health improvements broadly across its population, while the United States concentrates good outcomes among those with the most resources and lets others fall behind. The aggregate national figures reflect that difference.
What changed between 1985 and 2030
The shift in South Korean longevity is, by historical standards, extraordinarily rapid. According to the World Economic Forum’s coverage of the study, South Korean women born in 2030 will live, on average, 6.6 years longer than South Korean women born in 2010, the largest projected gain in any of the 35 countries studied. In 1985, South Korean female life expectancy was only 73.4 years. By 2010, it had risen to 84.2 years. By 2030, the projection adds another 6.6 years on top of that. The cumulative gain from 1985 to 2030 — a single generation — is approximately 17 years of additional average life expectancy.
The composition of those gains has changed over time. The earlier decades of South Korea’s longevity improvement were dominated by reductions in infectious disease mortality, particularly among children, as the country invested heavily in maternal and child health, vaccination programmes, and basic public health infrastructure. The more recent decades have been dominated by postponement of deaths from non-communicable chronic diseases — heart disease, stroke, cancer, diabetes, dementia. The earlier transition is one that other countries have made historically. The more recent transition is the one that is currently driving longevity gains in essentially every industrialised country, and South Korea is doing it faster and more equitably than most.
The 90-year ceiling and why it mattered
For much of the 20th century, demographers and gerontologists treated the 90-year mark as something close to a biological ceiling on average national life expectancy. The reasoning was partly empirical — no national population had ever come close to 90 — and partly theoretical, based on assumptions about the limits of human biological lifespan. According to ScienceDaily’s coverage of the Lancet paper, Ezzati noted that “as recently as the turn of the century, many researchers believed that life expectancy would never surpass 90 years.” The 2017 study explicitly framed itself as a challenge to that assumption. Its central finding was not that average longevity would continue increasing — that had been clear for decades — but that the 90-year barrier, long considered immovable, would in fact be crossed within roughly a generation.
The implications for healthcare, retirement, and social policy were substantial. A national population whose women live to an average of 90 years has a fundamentally different demographic structure from one whose women live to 80. The proportion of the population over 80, the duration of retirement, the demands on healthcare and elder-care systems, the labour-force participation rates of older adults, and the inter-generational economic transfers all shift substantially. The Ezzati team noted in their paper that policy responses to increased longevity would require investment in healthy ageing, healthcare and social care infrastructure, and possibly adjustment of retirement ages. South Korea, with its rapidly ageing population and one of the world’s lowest fertility rates, was already grappling with these issues before the 2017 projection appeared, and the demographic transition has continued in the years since.
What has happened since the projection
The 2017 study made its projections from 2010 baseline data and projected forward to 2030. As of 2026, the world is approximately four years from the projected outcome year, and the trajectory can be partially evaluated against actual data. The most recent World Health Organization figures show South Korean female life expectancy at approximately 86.7 years in 2024 — already at the level that, in 2012, was the highest in the world. The trajectory has been somewhat disrupted by the COVID-19 pandemic, which produced a small temporary dip in life expectancy in most countries before recovery, but South Korea handled the pandemic relatively well in mortality terms and the dip was modest. Whether the 90-year threshold is crossed exactly by 2030, or a year or two earlier or later, depends on continued trends in chronic disease mortality among elderly South Korean women that are difficult to project precisely.
The broader implication of the Lancet study has held up well in the years since publication. South Korea remains the most likely first nation to cross the 90-year average-female-life-expectancy threshold. France, Japan, Spain, and Switzerland remain in the next tier, with their own projections in the upper 80s. The United States has continued to fall behind its peer group in life expectancy gains, with widening internal inequalities and the additional negative impact of the opioid crisis having worsened rather than improved its position. The basic Ezzati framework — that broad-based socioeconomic equity, healthcare access, and modest population-level differences in BMI and blood pressure can produce dramatic national differences in longevity at the top end of human lifespan — has been substantially validated by the years since 2017. The 90-year threshold, which seemed nearly insurmountable when first projected, is now within a few years of being crossed.
