As we all know here, material conditions have progressively been getting worse and worse. Based on pretty much all political theory, crime rates should also be going up with worse material conditions. But they haven't, in fact, crime rates have been going consistently down for the past 30 or so years. Why is that?
The answer is: It's too complicated for anyone to know with any certainty if crime is actually decreasing, never mind the why. Anybody who can say with certainty about either is lying. Too many factors.