I have not seen any figures to support my thoughts but there could be a few main reasons
Political correctness and all the "isms"
By that I mean it has to be very difficult in the USA to keep the criminals off the streets when there are so many rules that the police are supposed to follow in making sure they don't infringe on a criminal rights
And following that, the criminals must believe that they are in paradise and so protected why should they worry about the slight chance that they will be convicted and serve time
This results in the public being convinced that it is not safe outside and that the authorities can no longer protect them so they have to do it themselves
So it could be that the screaming socialistic minorities are the cause.
