But they're probably wrong, too. Insurers have a lot of money riding on the actuarial tables, but they're still just a wisdom-of-crowds best guess. No one wil

But they're probably wrong, too. Insurers have a lot of money riding on the actuarial tables, but they're still just a wisdom-of-crowds best guess. No one will know what the true life expectancy was of everyone born this year until the last of them dies; similarly, no one will know the true remaining life expectancy of everyone who is currently 50 years old until the last of them dies. I agree that actuaries are taking into consideration a lot more data and experience than any HN armchair futurist, but that doesn't mean they're going to be right. Until the 1970s, most of the increase in life expectancy at birth was due to reductions in child mortality, which from an actuarial standpoint is not very interesting because it's rare for infants to have life insurance policies. The life expectancy of a 40-year-old didn't change much from 1850 until then (source: http://www.infoplease.com/ipa/A0005140.html http://www.infoplease.com/ipa/A0005140.html). In essence, nearly everyone now makes it to 40, and what's changed greatly since is what happens after that. The widespread concern is that it's not well understood whether that trend will continue, accelerate rapidly (and if so, whether the mean will increase, skew will increase, or both), or even reverse. Actuaries are professionals paid to make good guesses; they do it well, but they are not oracles.