More proof that the major reason for the drop in violent crime is. . . .
. . . . unleaded gasoline. Or more precisely, the phasing out of leaded gasoline in the US in the 1970s. You can easily find previous articles and evidence of this around the internet. Perhaps the most compelling evidence is that the drop in violence is entirely predictable based on when and how quickly leaded gasoline was phased out, regardless of the country. Here is the evidence as it relates to Britain, which phased out leaded gasoline much later than occurred in the US but, once it did so, did so much more quickly.
This isn't rocket science. We know what lead does to the brain, in terms of intellectual development and impulse control. That getting it out of the environment would have long term benefits for the children who grew up after lead was reduced or eliminated in their neighborhoods is entirely predictable and born out by the evidence.