Homicide rate at near 50-year low, probably thanks to low lead levels by @DavidOAtkins

Homicide rate at near 50-year low, probably thanks to low lead levels

by David Atkins

The nation's homicide rate is at its lowest point in nearly 50 years:

Things weren’t so hot for the American economy and a lot else in 2010, but for the health of the American people, it was a pretty good year.

Life expectancy improved, mortality rates fell for all five leading causes of death, and the homicide rate was as low as it has been in almost 50 years, according to data released Wednesday.

he gap in life expectancy between whites and blacks narrowed slightly, although the difference between men and women remained unchanged, at 4.9 years. Hispanic men and women continued to have the longest life expectancy, a finding that has puzzled demographers in recent years but that now appears to be unquestionable.

“We sort of expected those trends would continue, but what grabbed us here was the drop in homicide,” said Robert N. Anderson, chief of mortality statistics at the National Center for Health Statistics.

Homicide climbed into the top 15 causes of U.S. deaths in 1965. It placed tenth for three years in the early 1990s. In recent years, it has been hovering at 13 or 14. In 2010, it fell to 16.

“We’re really not sure what’s driving this. That’s the million-dollar question,” Anderson said.
What is driving it? There's still no agreement on the subject. Traditional liberal theories on crime would suggest that poverty should be correlated with criminal activity--that people turn to crime when they lack alternatives, and that people shy away from crime given better opportunities. And yet the numbers put the lie to those claims, and hence to a certain left-leaning views about criminal behavior and the reasons for it. Crime rate statistics have until recently been one of the very few feathers in the cap of rational conservatives to promote their worldview.

But it turns out that conservative arguments fail here as well. There is, of course, the theory popularized in Freakonomics that abortion is the cause of dropping crime rates. I never really bought into this, as the leap from correlation to causation seemed too great to be conclusive. Same goes for more conservative-leaning arguments about crack cocaine.

But one compelling thesis stands out, as bizarre as it may appear. It has to do with lead. Kevin Drum has been harping on this point for a while now, and the evidence is very compelling. The Washington Post had a great story on the connection between violent crime and lead levels in 2007:

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."

Through much of the 20th century, lead in U.S. paint and gasoline fumes poisoned toddlers as they put contaminated hands in their mouths. The consequences on crime, Nevin found, occurred when poisoning victims became adolescents. Nevin does not say that lead is the only factor behind crime, but he says it is the biggest factor.

Giuliani's presidential campaign declined to address Nevin's contention that the mayor merely was at the right place at the right time. But William Bratton, who served as Giuliani's police commissioner and who initiated many of the policing techniques credited with reducing the crime rate, dismissed Nevin's theory as absurd. Bratton and Giuliani instituted harsh measures against quality-of-life offenses, based on the "broken windows" theory of addressing minor offenses to head off more serious crimes.

Many other theories have emerged to try to explain the crime decline. In the 2005 book "Freakonomics," Steven D. Levitt and Stephen J. Dubner said the legalization of abortion in 1973 had eliminated "unwanted babies" who would have become violent criminals. Other experts credited lengthy prison terms for violent offenders, or demographic changes, socioeconomic factors, and the fall of drug epidemics. New theories have emerged as crime rates have inched up in recent years.

Most of the theories have been long on intuition and short on evidence. Nevin says his data not only explain the decline in crime in the 1990s, but the rise in crime in the 1980s and other fluctuations going back a century. His data from multiple countries, which have different abortion rates, police strategies, demographics and economic conditions, indicate that lead is the only explanation that can account for international trends.

Because the countries phased out lead at different points, they provide a rigorous test: In each instance, the violent crime rate tracks lead poisoning levels two decades earlier.

"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.

"In Britain and most of Europe, they did not have meaningful constraints [on leaded gasoline] until the mid-1980s and even early 1990s," he said. "This is the reason you are seeing the crime rate soar in Mexico and Latin America, but [it] has fallen in the United States."

Lead levels plummeted in New York in the early 1970s, driven by federal policies to eliminate lead from gasoline and local policies to reduce lead emissions from municipal incinerators. Between 1970 and 1974, the number of New York children heavily poisoned by lead fell by more than 80 percent, according to data from the New York City Department of Health.

Lead levels in New York have continued to fall. One analysis in the late 1990s found that children in New York had lower lead exposure than children in many other big U.S. cities, possibly because of a 1960 policy to replace old windows. That policy, meant to reduce deaths from falls, had an unforeseen benefit -- old windows are a source of lead poisoning, said Dave Jacobs of the National Center for Healthy Housing, an advocacy group that is publicizing Nevin's work. Nevin's research was not funded by the group.

The later drop in violent crime was dramatic. In 1990, 31 New Yorkers out of every 100,000 were murdered. In 2004, the rate was 7 per 100,000 -- lower than in most big cities. The lead theory also may explain why crime fell broadly across the United States in the 1990s, not just in New York.

What is it about lead that leads to violent crime? It's a neurotoxin that prevents impulse control:
The centerpiece of Nevin's research is an analysis of crime rates and lead poisoning levels across a century. The United States has had two spikes of lead poisoning: one at the turn of the 20th century, linked to lead in household paint, and one after World War II, when the use of leaded gasoline increased sharply. Both times, the violent crime rate went up and down in concert, with the violent crime peaks coming two decades after the lead poisoning peaks.

Other evidence has accumulated in recent years that lead is a neurotoxin that causes impulsivity and aggression, but these studies have also drawn little attention. In 2001, sociologist Paul B. Stretesky and criminologist Michael Lynch showed that U.S. counties with high lead levels had four times the murder rate of counties with low lead levels, after controlling for multiple environmental and socioeconomic factors.

In 2002, Herbert Needleman, a psychiatrist at the University of Pittsburgh, compared lead levels of 194 adolescents arrested in Pittsburgh with lead levels of 146 high school adolescents: The arrested youths had lead levels that were four times higher.

"Impulsivity means you ignore the consequences of what you do," said Needleman, one of the country's foremost experts on lead poisoning, explaining why Nevin's theory is plausible. Lead decreases the ability to tell yourself, "If I do this, I will go to jail."

Nevin's work has been published mainly in the peer-reviewed journal Environmental Research. Within the field of neurotoxicology, Nevin's findings are unsurprising, said Ellen Silbergeld, professor of environmental health sciences at Johns Hopkins University and the editor of Environmental Research.

"There is a strong literature on lead and sociopathic behavior among adolescents and young adults with a previous history of lead exposure," she said.

If true, there are two interesting conclusions one can draw:

1) Contra conservative claims, "tough on crime" statutes have had little to do with dropping crime rates. Instead, we can thank all those liberal hippie environmentalists for having the best crime prevention policies out there, and we can add violent murders to the list of costs that polluting corporations have externalized and forced society to pay for;


2) More disturbingly, contra claims from both liberals and conservatives alike, civilization seems to be a pretty thin veneer on human nature. If the difference between a rising wave of murders and record low crime rates, is simply a question of impulse control, that would mean that we all have moments where we would often like very much to do horrible things to people, but fear of reprisal and bouts of conscience get in the way just in time. It doesn't speak well for basic human nature, and serves as another data point for my earlier arguments about the guiding force behind liberalism as an idea.