



You guys are way too smart. I posted my mystery map of the Middle East yesterday morning, and in less than an hour you had figured out what it represented. For the rest of you, here’s the map with its real title:

I’m going to make an obvious point about this, but I want to make it carefully. Ever since I wrote my piece about the link between violent crime and leaded gasoline, I’ve gotten periodic questions about whether lead might be responsible for other things. The most common answer is maybe—but it’s unlikely we’ll ever have the data to prove it. For that reason, I try to stay pretty restrained about exactly what lead might and might not be responsible for.

That said, there’s a lot of evidence that leaded gasoline produced a wave of violent crime between 1960-1990 in the developed world, and that the introduction of unleaded gasoline eliminated that wave and eventually brought crime rates down nearly to 1960 levels. In most developed countries, leaded gasoline was phased out starting in the 70s and 80s, which benefited children born after that. When those children reached their late teenage years in the 90s and aughts, they were much less prone to impulsiveness and aggression, which led to lower crime rates.

But not every part of the world followed that timetable. In particular, leaded gasoline continued to be used in the Middle East up through the late 90s. Egypt began phasing it out in 1998, and most other countries followed over the next decade or so. Only a few—including Iraq and Afghanistan—still sell significant amounts of leaded gasoline.

Since lead poisoning affects infants, its affects show up about 18-20 years later. What this means is that in the bright red countries, the cohort of kids who reach their late teen years around 2020 should be significantly less aggressive and violent than previous cohorts. Around 2025 the countries in lighter red will join them. Around 2030 the countries in pink will join. By 2040 or so, the process will be complete.

Obviously this means that crime rates in the Middle East should decline steadily between 2020-40. But there’s more. Given the effects of lead, it seems almost certain that reducing lead poisoning in teenagers and young adults should lead to a decline in terrorism as well.

This is where I want to be careful. Obviously terrorism, like crime, has a lot of causes. What’s more, you could eliminate every molecule of lead in the world and you’d still have plenty of crime and plenty of terrorism. But you’d have less. If terrorism follows the path of violent crime, eliminating leaded gasoline could reduce the level of terrorism by 50 percent or more.

It’s also possible—though this is much more speculative—that effective terrorism requires a minimum critical mass of people who are drawn to it. If you fall below that minimum, it might wither away. In other words, it’s possible that removing lead from gasoline could reduce terrorism by even more than 50 percent.

In any case, this leads to a concrete prediction: Between 2020 and 2040, the level of terrorism emanating from the Middle East will drop by at least half. Ditto for violence more generally, including civil wars. In a decade or so, we should begin to get hints of whether this prediction is correct.