Researchers have proposed many theories to explain the huge drop in crime that started in the early 1990s. Some cite the legalization of abortion. Some think maybe it was cell phone use. Rudy Giuliani credits Rudy Giuliani.
At Mother Jones, Kevin Drum presents a strong case for another contender: lead.
The biggest source of lead in the postwar era, it turns out, wasn’t paint. It was leaded gasoline. And if you chart the rise and fall of atmospheric lead caused by the rise and fall of leaded gasoline consumption, you get a pretty simple upside-down U: Lead emissions from tailpipes rose steadily from the early ’40s through the early ’70s, nearly quadrupling over that period. Then, as unleaded gasoline began to replace leaded gasoline, emissions plummeted.
Intriguingly, violent crime rates followed the same upside-down U pattern. The only thing different was the time period: Crime rates rose dramatically in the ’60s through the ’80s, and then began dropping steadily starting in the early ’90s. The two curves looked eerily identical, but were offset by about 20 years.
Your first reaction to this may be similar to mine (and to Jess Zimmerman’s) — those graphs are a rough correlation, not a surefire link between lead and crime. Drum addresses that concern by citing research that isolated lead legislation and abatement, sometimes down to a city-block level.
Sure, maybe the real culprit [behind the crime drop] in the United States was something else happening at the exact same time, but what are the odds of that same something happening at several different times in several different countries?
[Economist Rick] Nevin collected lead data and crime data for Australia and found a close match. Ditto for Canada. And Great Britain and Finland and France and Italy and New Zealand and West Germany. Every time, the two curves fit each other astonishingly well. When I spoke to Nevin about this, I asked him if he had ever found a country that didn’t fit the theory. “No,” he replied. “Not one.”
Just this year, Tulane University researcher Howard Mielke published a paper with demographer Sammy Zahran on the correlation of lead and crime at the city level. They studied six US cities that had both good crime data and good lead data going back to the ’50s, and they found a good fit in every single one. In fact, Mielke has even studied lead concentrations at the neighborhood level in New Orleans and shared his maps with the local police. “When they overlay them with crime maps,” he told me, “they realize they match up.”
Drum then goes one step further, noting that the areas of the brain that lead affects are those that one might associate with criminal behavior: aggressiveness, impulsivity. With that, he rests his argument.
The argument isn’t a new one; we covered it in 2011. The argument presented by Drum is more robust, even if still not entirely persuasive.
The most important point comes last. Lead, in its various forms, is still a widely present pollutant, one that significantly impairs cognition and bone strength, particularly in pregnant women and young children. Regardless of how strong the link between crime and lead, there is a massive health benefit in reducing exposure. There’s an urgent need to curtail ongoing lead pollution.
A decade ago, I worked with a team that did lead abatement, repainting walls covered in lead paint and clearing the dust and chips that had flaked off. Even these small measures were considered to be crucial for the health of the often-low-income kids living in the homes.
Did cutting lead in gasoline spur a huge drop in crime? Possibly. Whether it did or not, there’s nonetheless huge value in removing lead from our environment.