[lvs]

This is likely just about population age distribution in prisons vs the general population.

16% of the US population is 65+, but only 2.7% in (federal) prisons. So that must account for a decent chunk of it.

https://www.bop.gov/about/statistics/statistics_inmate_age.j...

[subsubzero]

I agree that the age distribution does not match society in general, but take one thing into account, you have one group of people who have an extremely low death rate not in prison(children and teenagers) so this probably evens things out, extreme old age is not represented in prisons either, 80+ .