[adamzerner]

There is something I've never understood about this. Actually, I suspect that it is just plain old wrong.

It looks at what ages people died in the year 2019. If you die at age 80 in 2019, that means you were born in 1939. But if people born in the year 1939 are living to age 80... how do I put this... wouldn't you expect people born in, say, 1989 to live longer? Wouldn't people born 50 years later have longer life expectancies? Especially if you believe the stuff about accelerating rates of technogical growth.

[dasil003]

IANAA, but my assumption is that that is why they update the tables every year— we always have young cohorts with incomplete data, so the best we can do is extrapolate from the past. Given a fixed cohort, over time as new tables are generated and the cohort ages, the accuracy will converge to reality. You could then look at past tables retroactively to see the error in the original extrapolations (which could be large due to black swan events).

[mrtnmcc]

By choosing someone who died in 2019, you've implicitly chosen from the lucky group of survivors. This is not representative of everyone born in 1939. That is the discrepancy.

If you add the current age to the remaining years of life, the total lifespan is monotonically increasing. This is reflecting the fact you are only looking at the expected age of an increasingly dwindling group of lucky survivors.

[hugh-avherald]

Think of life expectancy as the expected age of death if you lived every year of your life in 2019.