Lead Poisoning and the Great 1960s Freakout: Rick Nevin, an economist not affiliated with a university, has gotten some publicity attributing the rise and fall of crime rates and the rise of illegitimacy to lead poisoning, since lead is known to reduce IQ and impulse control in children exposed to it. This is a theory with rather far-reaching implications, such as offering an explanation of the Great Freakout that began in America around the time of the Kennedy Assassination and the Beatles appearing on the Ed Sullivan Show and tapered off with surprising rapidity in the mid-1990s. The Washington Post claims:
"This study shows a very strong association between preschool blood lead and subsequent crime rate trends over several decades in the USA, Britain, Canada, France, Australia, Finland, Italy, West Germany, and New Zealand. The relationship is....consistent with neurobehavioral damage in the first year of life and the peak age of offending for index crime, burglary, and violent crime....Regression analysis of average 1985-1994 murder rates across USA cities suggests that murder could be especially associated with more severe cases of childhood lead poisoning."
This is a very interesting theory.
On the other hand, Japan, which had lots of lead-spewing cars and extremely dense population, and thus should have been a prime victim of lead poisoning, never experienced a Great Freakout. So, that's one strike against the theory.
In general, I'm skeptical of there being a "Single Bullet" explanation for the the 1960s, but it's worth looking at this in some detail, more than I can muster here, but I'll take a first look at it.
More generally, as Steven D. Levitt pointed out on his Freakonomics blog:
"Still, although both Post reporter Shankar Vendantam and the cited economist, Rick Nevin (whom I’d never heard of), appear quite convinced by the time-series data, I am not. When you have a variable like crime that goes up for a long time then goes down for a long time, it is easy to find other variables that share that pattern and appear to have a causal impact, even though the relationship is completely spurious."
Yet, Levitt goes on:
"About seven years ago, Michael Greenstone and I tried to look into this same issue using airborne lead measures at the local level, as well as other approaches. We ultimately gave up without finding anything. That largely soured me on the lead/crime link."
"Recently, however, Jessica Wolpaw Reyes at Amherst has put together what appears to me to be the most persuasive evidence to date in favor of a relationship between lead and crime. Rather than looking at a national time-series, she tries to exploit differences in the rates at which lead was removed from gasoline across states. I haven’t read her paper with the care that a referee would at an academic journal; but, at least superficially, what she is doing looks pretty sensible. She finds that lead has big effects (and, for what it’s worth, she also confirms that, when controlling for lead, the link between abortion and crime is as strong or stronger as in our initial study, which did not control for lead.)"
It's a long paper (70 pages) and a lot of good work went into it. After a quick read, though, I would venture to say that it has a couple of flaws. The first is that while it finds strong relationships among states over time between lead consumed in gasoline and overall published violent crime rates, it doesn't find much of a relationship between lead and murder. Dr. Wolpaw Reyes rationalizes:
"The weak murder results could also stem from the rarity of murders (rendering identification more difficult), a weaker effect of lead on murder than on other violent behavior, or a different functional form for this relationship (such as an increasing marginal effect). Given that murder is the most violent of violent crimes, it is not unreasonable to hypothesize that only substantial exposure to lead will produce this extremely aggressive and violent behavior, while more moderate exposure will have more moderate effects."
Uh ... Nah, I'm not at all persuaded that lead would influence people to be more impulsively violent but not more lethally impulsively violent. I don't see that as plausible.
The problem for how much confidence to place on this paper is that murder is the most accurately measured crime. Other crimes vary dramatically in likelihood of being reported to the police across time and place, but attention must be paid to a dead body with a hole in it.
Second, the big increase in the murder rate was from roughly 1965-1975. She assumes a 22 year lag, from postnatal exposure to lead, so that was from births in 1943 to 1955, but she says that lead poisoning due to leaded gasoline didn't peak until 1970, so how come the murder rate didn't keep going up? It bounced around a lot after that, but the Great American Freakout was basically from the mid-60s to the mid-70s. .
Here's her graph of "Gasoline Lead Exposure 1960 to 1990" (p. 66), which shows that lead from gasoline peaked in 1970. She writes: "Gasoline lead exposure rose until 1970 and then fell."
Third, when looking at the crime fall in the 1990s, this study appears to have the same flaw that dragged down Levitt's abortion-cut-crime theory -- a failure to look carefully at crime rates by age cohort, combined with an intoxication with analyzing complex state-level data that leads to a failure to do simple national-level reality checks. (She was clearly influenced by Levitt, so this shortcoming is not surprising.) Wolpaw Reyes simply assumes a 22 year lag between lead poisoning around the time of birth and the violent crime rate. But, we can easily look at more detailed data for different age cohorts, which shows that the crime decline of the 1990s began among older individuals, not among the younger people supposedly benefiting from lower lead or higher abortion.
If you assume a 22 year lag to violent crime, then this graph looks great because the murder rate started to fall after about 1991.
But, that's the same mistake Levitt made way back in 1999: he forgot to look at the crime rates among narrower age cohorts. For the 17-and-under crowd, the two worst years were 1993-94. In other words, they were born when lead pollution had already fallen by almost half (just as they were born when legal abortion was close to its peak, which is a problem for Levitt's theory).
Here's the relevant homicide rate graph showing that for the 14-17 year-old cohort, the murder rate moved in exactly the wrong direction for the first 6-7 years of the great lead decline.
Similarly, here's the non-lethal serious violent crime rate for 12-17 year-olds as reported by the government's massive annual survey of crime victims. It too shows the crime rate for the relevant cohort moving in the wrong direction.
Now, this hardly disproves the lead-crime theory, it just subjects it to an obvious reality check, which demonstrates a lack of care over looking at the precise age of criminals. Now, it could well be that the crack wars overwhelmed the lead effect at the national scale. Or, it could be that lead has an impact, but it's strongest at an older age, like 6 or 7. Or, her graph showing a lead peak in 1970 is inaccurate (other sources suggest a slightly later peak).
On a side note, Levitt also writes:
Besides discussing lead and crime in Massachusetts' towns, Masters writes:
"2. Communities using either fluosilicic acid (H2SiF6) or sodium silicofluoride (NaSiF6) have significantly higher rates of crime than those using sodium fluoride or delivering unfluoridated water (with the exception of towns with naturally fluoridated water).
"3. The use of fluosilicic acid (H2SiF6) to fluoridate public water supplies significantly increases the amounts of lead in the water (whereas the use of sodium silicofluoride (NaSiF6) or sodium fluoride (NaF) does not."
In other words, if Dr. Masters is not mistaken, Col. Jack D. Ripper in "Dr. Strangelove" was right: fluoridation is poisoning our precious bodily fluids.
(Wandering even farther afield, Jack D. Ripper was played, brilliantly, by Sterling Hayden, the stepfather of American Conservative editor Scott McConnell.)