See, it specifically goes by "prison population," which is a massive weasel number since it relies entirely on the number of prisoners rather than things like the population sizes of countries, and the fact that the largest country on earth actively metes out capital punishment for the pettiest of crimes. You can't take a continent-sized country with a developed justice system and be shocked when it houses a lot of criminals rather than killing people for petty theft.
Also the whole "political prisoners" thing compared to arresting murderers, but I digress