Comment by immibis

The USA should do, perhaps, four fifths of that. Despite having 4% of the world's population it has 25% of the world's prisoners, and one of the highest crime rates in first-world countries so it'd obviously not working.

They could also consider banning substances that make people more aggressive... There's a particular artificial pesticide whose name I don't remember, which is coincidentally banned in all the places with much lower crime rates, and has been shown to alter behaviour in monkeys.