New research reveals that the extraordinary surge in human life expectancy throughout the twentieth century may not be sustained for later generations.

Drawing on extensive mortality records spanning twenty‑three affluent countries—including the United States, Japan, Canada, Australia and Western European nations—the study projects that individuals born between 1939 and 2000 are unlikely to reach an average lifespan of one hundred years.

This follows a lengthy period when each birth cohort outlived the previous one by nearly half a year on average. 

The analysis shows that life expectancy gains have slowed by between thirty‑seven to fifty‑two percent compared with earlier trends—dropping from an average increase of five and a half months per generation between 1900 and 1938 to roughly two and a half to three and a half months per generation thereafter. This deceleration is largely attributed to the fact that the significant early‑century improvements were driven by sharp reductions in infant and child mortality—gains that are now largely exhausted—while advances at older ages are insufficient to compensate. 

Even in scenarios where adult survival improves at twice the expected rate, gains in life expectancy would remain below those achieved in the early twentieth century. The researchers emphasise that this plateau in longevity—the end of the ‘automatic’ generational improvements—poses major challenges for health and retirement systems.

They call for a policy shift focused on enhancing the quality of life for older populations, preventing chronic illness, and adapting pensions and social services to the new reality. 

The findings underscore an imperative for governments to revisit assumptions around continually rising longevity and to invest strategically in healthy aging initiatives in place of relying on life expectancy projections that may no longer hold.