The problem with looking at crime rate statistics is that they only tell you about reported crime levels. If everyone knows that a petty theft, or a mugging, or a minor assault isn't going to be investigated or prosecuted then people stop bothering to report it.

This is referred to as the "dark figure of crime" by sociologists (https://en.m.wikipedia.org/wiki/Dark_figure_of_crime) which sounds a bit like a description of Batman.