Mother Jones' writer Kevin Drum has a very, very, very interesting article on decrease of crime as it co-relates to lead in gasoline.
The essential bit for me:
Experts often suggest that crime resembles an epidemic. But what kind? Karl Smith, a professor of public economics and government at the University of North Carolina-Chapel Hill, has a good rule of thumb for categorizing epidemics: If it spreads along lines of communication, he says, the cause is information. Think Bieber Fever. If it travels along major transportation routes, the cause is microbial. Think influenza. If it spreads out like a fan, the cause is an insect. Think malaria. But if it's everywhere, all at once—as both the rise of crime in the '60s and '70s and the fall of crime in the '90s seemed to be—the cause is a molecule.
Sure, this is econometrics, a new science and a heavily disputed one. And Drum writes well, I admit that his evidence convinces me. As does the Skeptic blog post that I read next.