Landmark Study Warns: We May Never See Average Lifespans Hit 100

12:14:55

2025-10-13

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A recent study co-authored by a University of Wisconsin-Madison professor shows that the rapid improvements in life expectancy achieved by high-income countries during the first half of the 20th century have slowed considerably. The research concludes that, on average, no generation born after 1939 will reach a life expectancy of 100 years.

The work, published in the Proceedings of the National Academy of Sciences, was conducted by Héctor Pifarré i Arolas of the La Follette School of Public Affairs, José Andrade of the Max Planck Institute for Demographic Research, and Carlo Giovanni Camarda of the Institut national d’études démographiques. Their analysis examined life expectancy trends across 23 high-income, low-mortality countries using data from the Human Mortality Database and applied six separate mortality forecasting models.

“The unprecedented increase in life expectancy we achieved in the first half of the 20^th century appears to be a phenomenon we are unlikely to achieve again in the foreseeable future,” according to Pifarré i Arolas. “In the absence of any major breakthroughs that significantly extend human life, life expectancy would still not match the rapid increases seen in the early 20th century, even if adult survival improved twice as fast as we predict.”

Historical trends in longevity

Between 1900 and 1938, life expectancy increased at a rate of roughly five and a half months with each successive generation. In high-income countries, someone born in 1900 could expect to live an average of 62 years, while by 1938 the average lifespan had risen to about 80 years under similar conditions.

For those born from 1939 to 2000, however, the pace of improvement slowed considerably, averaging only two and a half to three and a half months per generation depending on the model used. Mortality forecasting methods—statistical tools that use past and present mortality data to project future trends—allowed the researchers to estimate how life expectancy might evolve under a range of realistic scenarios.

Why future gains are limited

“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. This decline is largely due to the fact that past surges in longevity were driven by remarkable improvements in survival at very young ages,” according to corresponding author Andrade.

At the beginning of the 20th century, infant mortality fell rapidly due to medical advances and other improvements in quality of life for high-income countries. This contributed significantly to the rapid increase in life expectancy. However, infant and child mortality are now so low that the forecasted improvements in mortality in older age groups will not be enough to sustain the previous pace of longevity gains.

While mortality forecasts can never be certain as the future may unfold in unexpected ways – by way of pandemics, new medical treatments, or other unforeseen societal changes – this study provides critical insight for governments looking to anticipate the needs of their healthcare systems, pension planning, and social policies.

Although a population-level analysis, this research also has implications for individuals, as life expectancy influences personal decisions about saving, retirement, and long-term planning. If life expectancy increases more slowly as this study shows is likely, both governments and individuals may need to recalibrate their expectations for the future.