Kevin Drum’s new article about crime and leaded gasoline is a must-read:
Put all this together and you have an astonishing body of evidence. We now have studies at the international level, the national level, the state level, the city level, and even the individual level. Groups of children have been followed from the womb to adulthood, and higher childhood blood lead levels are consistently associated with higher adult arrest rates for violent crimes. All of these studies tell the same story: Gasoline lead is responsible for a good share of the rise and fall of violent crime over the past half century.
When differences of atmospheric lead density between big and small cities largely went away, so did the difference in murder rates.
Like many good theories, the gasoline lead hypothesis helps explain some things we might not have realized even needed explaining. For example, murder rates have always been higher in big cities than in towns and small cities. We’re so used to this that it seems unsurprising, but Nevin points out that it might actually have a surprising explanation—because big cities have lots of cars in a small area, they also had high densities of atmospheric lead during the postwar era. But as lead levels in gasoline decreased, the differences between big and small cities largely went away. And guess what? The difference in murder rates went away too. Today, homicide rates are similar in cities of all sizes. It may be that violent crime isn’t an inevitable consequence of being a big city after all.
The gasoline lead story has another virtue too: It’s the only hypothesis that persuasively explains both the rise of crime in the ’60s and ’70s and its fall beginning in the ’90s. Two other theories—the baby boom demographic bulge and the drug explosion of the ’60s—at least have the potential to explain both, but neither one fully fits the known data. Only gasoline lead, with its dramatic rise and fall following World War II, can explain the equally dramatic rise and fall in violent crime.
Regulations that eliminated leaded gasoline almost certainly have had a ridiculously high benefit-to-cost ratio, and as Kevin says programs to eliminate other sources of emissions from lead would too.
I don’t know if this was true in the United States, but one interesting thing to me is that growing up in an oil-producing province the phase-out of leaded gasoline was a major culture war issue, producing a lot of opposition. I suspect that if this issue came up today the Republican Party would be uniformly opposed to eliminating lead in gasoline and could have prevented it for years.