This happened right before the cultural revolution https://en.m.wikipedia.org/wiki/Great_Chinese_Famine might have helped cut down the potential prison population...
Edit, digging this up from 5 threads deep:
...I understand what per-100,000 means, but I also understand that not all groups of 100,000 people are the same; removing a large sub-population of people that doesn’t exactly match the overall population’s average will result in a change to the overall population average.
If you have a total population (T), and you are measuring the rate of an event (E), then E / T gives your average event rate for the total population, which you can then normalize to a per-X number. For example: T = 1000 people E = 10 incarcerations. 10 / 1000 = .01, normalized to per 100 capita would be 1 per 100 people on average, from the total population.
If you have a sub-demographic in that population (Ts), and it has a different rate of an event (Es) then its rate is also Es / Ts. For example: Ts = 100 poor-people Es = 5 incarcerations. 5 / 100 = .05, normalized to a per 100 capita would be 5 people per 100 on average, for that sub-population.
If you suddenly remove that sub-population, what happens to the rate of the overall population? That’s easy to calculate: (E - Es) / (T - Ts) (10 - 5) / (1000 - 100) = 5 / 900 = .0055, normalized to a per 100 capita would be .55.
Suggesting that a sub-demographic doesn’t perfectly match the per-capita average of an entire population and that removing them would change the overall per-capita rate isn’t nonsense.