July 9, 2007

Did getting the lead out of gasoline, not legalized abortion, cause crime to fall? From the Washington Post:

The theory offered by the economist, Rick Nevin, is that lead poisoning accounts for much of the variation in violent crime in the United States. It offers a unifying new neurochemical theory for fluctuations in the crime rate, and it is based on studies linking children's exposure to lead with violent behavior later in their lives.

What makes Nevin's work persuasive is that he has shown an identical, decades-long association between lead poisoning and crime rates in nine countries.

"It is stunning how strong the association is," Nevin said in an interview. "Sixty-five to ninety percent or more of the substantial variation in violent crime in all these countries was explained by lead." ...

"It is startling how much mileage has been given to the theory that abortion in the early 1970s was responsible for the decline in crime" in the 1990s, Nevin said. "But they legalized abortion in Britain, and the violent crime in Britain soared in the 1990s. The difference is our gasoline lead levels peaked in the early '70s and started falling in the late '70s, and fell very sharply through the early 1980s and was virtually eliminated by 1986 or '87.

It would be interesting to see Nevin's new data. Here's an old article. (I haven't read it yet.) And here's a newspaper article about another researcher's lead-IQ-crime connection.

Abortions can be assigned to very precise times, which quickly allowed big doubts to be raised about Steven D. Levitt's abortion-cut-crime theory, since the cohort born soon after legalization had much higher murder rates. Lead is a little slipperier to analyze, because it hangs around in the environment, perhaps providing wiggle room for the analyst if the chronology doesn't quite match up.

The WaPo article ignores Nevin's link of lead to lowering IQ, as in this 2000 article. That ingesting lead makes you stupider was known for a long time. In James T. Farrell's 1930s novels about Chicago prole Studs Lonigan, Studs and his pals debate whether to give up the good pay of working as painters because all the old painters seem pretty dim from exposure to lead paint.

Meanwhile, Modern Dragons offers another potential source of influence on human behavior, one that's been analyzed even less: gut flora.

My published articles are archived at iSteve.com -- Steve Sailer


Unknown said...

Lead might account for the disdain of urban blacks for "bamas". The bamas were more peaceful, not because of a history of obedience, but because there was less lead in the country than in the city.

It might account for why immigrant hispanics, often indigenous folk from the deep country of Mexico and S. America, are less violent than native born.

A rich mine for speculation on many topics.

Anonymous said...

The gut flora paper was fascinating. Thanks for the introduction to Mike Johnson, a very intelligent young person. Twin studies, as Johnson suggests, would be very interesting to see the results on diet to all sorts of human performance markers and physical manifestations.

Anonymous said...

I think that's probably the case and, getting further afield, what I'd like to do is attempt to look into whether the changes in gut ecosystems caused by changes in eating habits and food manufacturing trends- aggregated over the 300 million people who live in America- could contribute to a stochastic change in national character. Perhaps a significant contributing factor to some of our institutional ills is the food we eat, the corresponding imbalance in gut flora which arises from eating such food, and the subtle yet powerful-in-aggregate dysfunctional personality changes that e.g., biologically-active metabolites of such non-symbiotic gut flora might cause.

Yes! This is something I've been wondering myself.

I've seen some of the studies he's mentioned previously. Here are a couple of references to other studies that I'm aware of:


Animal studies suggest that gut flora may contribute benzodiazepine ligand activity, as well as increased benzodiazepine receptor agonist activity.

Postnatal microbial colonization programs the hypothalamic-pituitary-adrenal system for stress response in mice.

There are also a lot of questions about the effect of gut flora on the immune system:

Finally, there was an issue of Science magazine which discusses the gut-brain connection:

I haven't seen it, though.

Anonymous said...

I agree the gut flora stuff was interesting. (Note to self:Buy yogurt!) The part about the bacteria causing the rat to seek out cat urine,so the poor rat could be eaten,was like something from the Twilight Zone! (Remember "To Serve Man"?? :D )

Anonymous said...

Oh, and I forgot about this: there has long been suspicion that Toxoplasma gondii may play a role in schizophrenia.

Anonymous said...

From the article:
"Nevin's finding implies a double tragedy for America's inner cities: Thousands of children in these neighborhoods were poisoned by lead in the first three quarters of the last century. Large numbers of them then became the targets, in the last quarter, of Giuliani-style law enforcement policies."

I'm not a huge Giuliani fan, but that's pretty disgusting. The article itself admits that Giuliani contributed 10-20% to the fall in violent crime in New York - that's 150-300 murders a year less than the 1990 peak!

Anonymous said...

The article seems a desperate attempt to spin away: tough enforcement + decline of drug turf wars + thugs in jail = less crime.

Occam's Razor suggests the simplest explanation is the most fit explanation.

Fewer people committing crimes because they are dead, in jail, or won turf wars seems about right to me.

What's really eating at the WaPo article is the elitism that pushes the morally superior rich over Joe Average.

Anonymous said...

Have Philadelphia's lead poisoning rates remained high? After all, Philadelphia continues to have a significant homicide rate.

Unknown said...

Lead may make a person stupid and eventually kill him, but there is no evidence it makes anyone violent or crime-minded. Further, there is no really good correlation between leaded gasoline and blood levels of lead!

Aviation gasoline still contains lead, and in colossal amounts-such that one pint of avgas in 10 gallons of unleaded car gas will boost octane ratings five or more points. Are people working around piston-engine aircraft generally rendered stupid?

Anonymous said...

Remember the 1970s PSAs urging kids not to eat lead paint? In the background, spooky atonal "horror" music played while a tot in slow-motion chewed long gulping pieces of what looked like paint strips, ruining his mind... Terrifying! But if a kid eats paint, he has to be pretty stupid to begin with, I think.

I don't know if fingernail polish contains lead, but my ex-wife used to become virtually retarded for hours after applying it. I made her stop.

Anonymous said...

I don't know if fingernail polish contains lead

Try acetone.

Anonymous said...

reseauplate's post is all wet. Avgas 100LL contains 2 grams lead per gallon. High octane street gasoline of the late 60s had about 4 grams per gallon. And no, one pint Avgas will not raise street gasoline by 5 points. Duh.

As for the anecdote about the painter's exposure to lead. I think it is more to do with the VOCs of oil based paints that were more common before latex paints. This was also true in the days of laquers used by automobile painters. The stuff is like sniffing glue or other VOCs.

Anonymous said...

Green-100/130-avgas does indeed contain monster amounts of lead. It is still available on the market-if you buy 10,000 gallons, they will make up anything from 80/87 (red) to 115/145 (purple) you want. FBOs in the Northwest tend to carry it.