For much of the 20th century, people in wealthy countries saw their life expectancy rise at an extraordinary pace.
Advances in medicine, hygiene, and living conditions meant that each new generation could expect to live years longer than the one before it.
But according to a new study, those dramatic gains have slowed sharply, and the dream of average lifespans reaching 100 years now looks unlikely.
The study, published in the Proceedings of the National Academy of Sciences, was led by Héctor Pifarré i Arolas of the University of Wisconsin–Madison, José Andrade of the Max Planck Institute for Demographic Research, and Carlo Giovanni Camarda of the Institut national d’études démographiques.
The researchers analyzed mortality records from 23 high-income countries using six different forecasting methods to track how life expectancy has changed over time and where it might be heading.
The results show a clear pattern.
From 1900 to 1938, life expectancy in high-income countries rose by about five and a half months with every new generation. A child born in 1900 could expect to live around 62 years on average. By 1938, that figure had leapt to 80 years.
The jump reflected massive improvements in early life survival, as childhood diseases and infant mortality rates plummeted thanks to better vaccines, antibiotics, sanitation, and nutrition.
But for generations born after 1939, the pace of improvement slowed dramatically. Between 1939 and 2000, life expectancy rose by only about two and a half to three and a half months per generation, depending on the forecasting model used. That rate is nowhere near enough to push average lifespans to 100 years.
“We forecast that those born in 1980 will not live to be 100 on average, and none of the cohorts in our study will reach this milestone,” says Andrade.
“The key reason is that the dramatic leaps of the past were driven by major improvements in survival at young ages. Today, childhood mortality in high-income countries is already extremely low, so there is less room for those gains.”
The researchers note that even if survival among adults improved twice as fast as current predictions suggest, it still would not match the rapid increases seen in the early 20th century. Without groundbreaking medical advances to slow aging or radically extend life, average life expectancy is unlikely to accelerate in the same way again.
While forecasts can never be perfect—future events such as pandemics, medical breakthroughs, or social changes could alter the picture—the findings carry major implications for governments and individuals.
Slower growth in life expectancy affects how societies plan for pensions, healthcare, and long-term care. For individuals, it influences decisions about retirement savings and how to plan for later life.
“The extraordinary gains of the past were unique to their time,” says Pifarré i Arolas. “This study reminds us that expectations for the future must be realistic and adjusted to today’s demographic realities.”
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