America’s Real Criminal Element: Lead
Why are violent crime rates still dropping, even during the recession? The latest evidence suggests lead—in the air, in our gasoline, in our paint—was responsible for the rise in crime in the 1960s & ’70s, and the drop in the 1990s:
“And with that we have our molecule: tetraethyl lead, the gasoline additive invented by General Motors in the 1920s to prevent knocking and pinging in high-performance engines. As auto sales boomed after World War II, and drivers in powerful new cars increasingly asked service station attendants to ‘fill ‘er up with ethyl,’ they were unwittingly creating a crime wave two decades later.
“It was an exciting conjecture, and it prompted an immediate wave of…nothing. Nevin’s paper was almost completely ignored, and in one sense it’s easy to see why—Nevin is an economist, not a criminologist, and his paper was published in Environmental Research, not a journal with a big readership in the criminology community. What’s more, a single correlation between two curves isn’t all that impressive, econometrically speaking. Sales of vinyl LPs rose in the postwar period too, and then declined in the ’80s and ’90s. Lots of things follow a pattern like that. So no matter how good the fit, if you only have a single correlation it might just be a coincidence. You need to do something more to establish causality.”