America’s incarceration rate is in decline

Freakonomics argued that crime correlates to whether or not abortion is available.

If it is not, crime rates are up, and by a lot.

If it is, crime rates are down.

When you flip from one to the other, takes about 15/20 years for the effect to show up.

Rationale is that forcing parents to have their kids when they're not ready for them significantly increases delinquency in young adults.

This is apparently the only possible theory at the moment. It's not proven, of course, but the other theories which were given have been found lacking. This is the only theory which has some evidence, and hasn't been found to be wrong.

I doubt there is a single explanation. I think it's multiple factors.

Unleaded gasoline could also be a factor. Every country has shown drops in crime rates when leaded gasoline was phased out.

If I recall, leaded gasoline was phased out in the 80ies, which fits a drop in crime rates in the 90ies.

Availability of pornography has cut down the rate of rapes significantly. Too bad the republicans are going to try to ban all porn pretty soon, according to their stated agenda. They do love their wealthy donors that run the prison-industrial-complex.