Lead poisoning due to leaded gasoline has been one of the more interesting (and common sense) explanations of that rise and fall of crime.

And it's almost certainly bullshit. There is no correlation with crime rates and lead exposure. The pattern observed is a massive spike in crime during the '80s and '90s due to gang activity from the crack boom, which then falls back down to '60s/'70s levels afterward. What you'd expect to see if lead exposure was the problem is a very gradual increase over time and then a gradual tail off as exposure reduced. Instead the homicide rate doubled for folks under 25 between 1983 and 1993, and then fell back to 1980s levels by the early 2000s.

The background crime rate increase from the 1960s forward is more readily explained by societal changes, as well as the start of the "war on drugs".

Relevant article: http://www.motherjones.com/environment/2013/01/lead-crime-li...

the "Crack Epidemic" really didn't start till 1984. Though this doubled the murder rates in teens in minority groups it doesn't explain the 1970 - 1984 rise. Though the lead gasoline seems crazy but very interesting.

I suppose one could make the argument that one reason for the decline in crime rates is due to the fact that so many criminals are in prison. I don't necessarily agree with that, but the argument could be made.

But I've been led to believe that a large amount, if not majority, of drug crime prisoners are due to low-level and non-violent criminal acts. Many of the drug laws are extremely heavy-handed that puts many people in prison for little reason. If that's the case, I doubt most of these people would have contributed to violence statistics.