Humanity is hitting the upper limit of life expectancy, according to a new study.

Advances in medical technology and genetic research—not to mention larger numbers of people making it to age 100—are not translating into marked jumps in lifespan overall, according to researchers who found shrinking longevity increases in countries with the longest-living populations.

“We have to recognize there’s a limit” and perhaps reassess assumptions about when people should retire and how much money they’ll need to live out their lives, said S. Jay Olshansky, a University of Illinois-Chicago researcher who was lead author of the study published by the journal Nature Aging.

“We are reaching a plateau” in life expectancy, he agreed. It’s always possible some breakthrough could push survival to greater heights, “but we don’t have that now,” said Mark Hayward, a University of Texas researcher.

Life expectancy is one of the world’s most important health measures, but it is also imperfect: It is a snapshot estimate that cannot account for deadly pandemics, miracle cures, or other unforeseen developments that might kill or save millions of people.

In the new research, Olshansky and his research partners tracked life expectancy estimates for the years 1990 to 2019, drawn from a database administered by the Max Planck Institute for Demographic Research. The researchers focused on eight of the places in the world where people live the longest—Australia, France, Hong Kong, Italy, Japan, South Korea, Spain, and Switzerland.

The study suggests that there’s a limit to how long most people live, and we’ve about hit it, Olshansky said. “We’re squeezing less and less life out of these life-extending technologies. And the reason is, aging gets in the way,” he said.

It may seem common to hear of a person living to 100. In 2019, a little over 2% of Americans made it to 100, compared with about 5% in Japan and 9% in Hong Kong, Olshansky said.

It’s likely that the ranks of centenarians will grow in the decades ahead, experts say, but that’s because of population growth. The percentage of people hitting 100 will remain limited, likely with fewer than 15% of women and 5% of men making it that long in most countries, Olshansky said.

This article was provided by The Associated Press.