Did Unleaded Gasoline Improve Educational Outcomes?


One of my Twitter followers, @archeratlarge, asks:

Has anyone applied @kdrum’s analysis of lead and crime to education outcomes?

I get asked this a lot, and it’s a slow news day, so I’m going to semi-answer this. As it happens, a little bit of work has been done on this question, but not much. And there’s a pretty good reason for that.

At first glance, this seems like an obvious thing to look at. The jury may still be out on the connection between lead and crime, but it’s certainly not on lead’s general effect on developing brains. There’s overwhelming, and universally accepted evidence that exposing children to high lead levels reduces their IQs and contributes to learning disabilities. So reducing exposure to lead, as we did by introducing unleaded gasoline between 1975 and 1995, certainly ought to show up in school test scores, graduation rates, and so forth.

But there’s an analytic problem that makes it hard to measure this. Let’s take a look at crime first. Very few people are potential violent criminals. If you plot criminal tendencies on a bell curve, perhaps the rightmost 3 percent or so are likely to actually commit murder, rape, or assault.

But when you expose huge numbers of children to lead, as we did with leaded gasoline after World War II, what you’re essentially doing is moving the bell curve to the right. For most people, that makes very little difference. But for a few who were already on the edge, it pushes them over into a life of violent crime. And when you move a bell curve, the area under the rightward tail increases a lot. The diagram below illustrates this:

What this means is that a small effect from lead can have a very big effect on the level of violent crime. Crime rates will double or triple, and this makes it amenable to statistical study. Because crime has so many different causes, it’s still not easy to figure out what happened, but at least it’s possible.

Education is exactly the opposite. In this case, we’re dealing with big groups (nearly everyone graduates from high school) or averages (test scores, for example). Those move only slightly when the bell curve moves to the right:

You can see the problem. If, say, the average score on a test improves from 300 to 307 over the course of 20 years, it’s too small an effect to isolate. The same is true if graduation rates increase from 75 percent to 79 percent. There are dozens of things that could plausibly cause this, and figuring out a way tease out the individual contribution of lead is all but impossible.

The decline of leaded gasoline almost certainly had an effect on educational outcomes. I’d guess that essentially no one doubts this. But because you’re studying an entire student population, not just a tiny fraction at the right end of a bell curve, the effect is too small to study. It’s probably there, but we’re unlikely to ever put a number to it.

DOES IT FEEL LIKE POLITICS IS AT A BREAKING POINT?

Headshot of Editor in Chief of Mother Jones, Clara Jeffery

It sure feels that way to me, and here at Mother Jones, we’ve been thinking a lot about what journalism needs to do differently, and how we can have the biggest impact.

We kept coming back to one word: corruption. Democracy and the rule of law being undermined by those with wealth and power for their own gain. So we're launching an ambitious Mother Jones Corruption Project to do deep, time-intensive reporting on systemic corruption, and asking the MoJo community to help crowdfund it.

We aim to hire, build a team, and give them the time and space needed to understand how we got here and how we might get out. We want to dig into the forces and decisions that have allowed massive conflicts of interest, influence peddling, and win-at-all-costs politics to flourish.

It's unlike anything we've done, and we have seed funding to get started, but we're looking to raise $500,000 from readers by July when we'll be making key budgeting decisions—and the more resources we have by then, the deeper we can dig. If our plan sounds good to you, please help kickstart it with a tax-deductible donation today.

Thanks for reading—whether or not you can pitch in today, or ever, I'm glad you're with us.

Signed by Clara Jeffery

Clara Jeffery, Editor-in-Chief

We Recommend

Latest

Sign up for our newsletters

Subscribe and we'll send Mother Jones straight to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate

Share your feedback: We’re planning to launch a new version of the comments section. Help us test it.