The US has one of the highest, if not THE highest incarceration rate in the world. Maybe the reason crime is dropping is the obvious one, we are putting more people in jail and keeping them there longer. But what happens when they all get out?

I have another theory, too. I don't believe people commit crimes because they are poor and need to eat. Food is cheap. People commit more rcrimes because they live in a society where there is a greater disparity of wealth, and people want their share. The poor don't steal to buy bread, they steal to buy designer tennis shoes, bling and big stereos and flashy wheels for their cars. White collar criminals are similarly driven, but their bling is different.

Drugs are also a major driving factor. If drugs were cheap crime would go down, Addicts could get their fix without stealing, and pushers would find dealing less profitable. Until all the factors are identified, their effects and interactions properly weighted, and comprehensive sociometric models developed and tested, we probably won't know for sure.

This is why we need sociologists, and they need to be trained to do the research and the analysis, not justify their pet ideological preconceptions.

PS: Leaded gas may have been introduced in the 20s, but automobile ownership didn't really take off until the 50s.