The graph below is not a sign of cause an effect, but it certainly tells a story. It strongly suggests that increasing the prison population reduces crime. We would need prison numbers from before 1990 to really get a feeling for it.
You can see crime reducing as the prison population increases.
- In general, prison numbers relate to the amount of crime
- However, it is possible (in the short term at least) to reduce crime by increasing prison numbers
- It is also possible to increase crime by reducing prison numbers
It is obvious that locking up a serial crim will reduce crime. The argument is really only about locking up the first-time crims who are not going to offend again and have fully paid back any debt.
I agree that we should avoid that, but then of course, we do. It takes quite a bit of crime before someone is locked up, and then they only get a few months.