For a couple of generations now people have been pushing the idea that the "root causes" of crime are social problems like poverty, income inequality, discrimination, and so on.
I'm of the opinion that this is all nonsense and always has been, but it's a difficult proposition to refute - we just don't get natural experiments that allow one to test this very often.
Katrina gave us one a few years ago: murder rates dropped by 100% for a period of 3 months after Katrina (yes, you read that percentage correctly).
The Baltimore example is that over the period of the recent blizzards – when most potential victims were stationary, and not accessible to the police, the crime rate dropped.
For example, murders – of which there were 18 in the first 37 days of the year – dropped to 0 in 9 days.
Statistically, that’s close to impossible – akin to flipping 9 heads in a row (try it: you’ll get bored before you do it). That is, unless there is some interfering factor.
In this case, it was that potential murderers were not intersecting with potential victims over those 9 days.
This sort of natural experiment should make it fairly clear that crime is about interactions between criminals and other people, rather than root causes that might leave those criminals with … low self-esteem.
It also should make it clear that policing isn’t that much of crime preventive. I hate to point it out, and the police did too. They’d probably be the first to point out that they couldn’t patrol during the blizzards like they do on most days. Perhaps policing is better viewed as reactionary.