And that is repeated, violent crime. Because you have to have something wrong with you to be the perpetrator of repeated violent crime. Thankfully such people are a small minority.
By locking up the people who are the perpetrators of repeated violent crime you reduce the chance of it happening currently and because you have shown a commitment to hunt down and punish people like that you have prevented future crime.
The underlying cause of crime is the conviction that you will get away with it. Remove that conviction and you have reduced the number of people who commit crimes.
At this point the amount of criminal activity has been reduced to a level that it can be dealt with easily.
I look at these reports warily due to governments categorizing serious crimes as lesser crimes, dismissing lesser crimes altogether and failing to report crimes perpetrated in certain zones because they lack (or won’t apply) the manpower to do the job - because it makes the departments look bad.
This can be directly attributed to cities hiring chiefs from other areas - for PR using too much money - rather than promoting up from within the ranks. That puts politicians above policemen who protect “the image” more than the populace.