Lead and crime

I’ve been meaning to do a quality post about the recent– and very surprising to criminologists– drop in the crime fate.  Since, I’ve failed to get around to it, time to just mention that most interesting thing I’ve read on the matter.  Famous and groundbreaking criminologist James Q. Wilson suggests that a very significant portion of the drop in crime can be explained by the fact that we’ve removed a (metaphorical) ton of lead from our environment in recent decades:

There may also be a medical reason for the decline in crime. For decades, doctors have known that children with lots of lead in their blood are much more likely to be aggressive, violent and delinquent. In 1974, the Environmental Protection Agency required oil companies to stop putting lead in gasoline. At the same time, lead in paint was banned for any new home (though old buildings still have lead paint, which children can absorb).

Tests have shown that the amount of lead in Americans’ blood fell by four-fifths between 1975 and 1991. A 2007 study by the economist Jessica Wolpaw Reyes contended that the reduction in gasoline lead produced more than half of the decline in violent crime during the 1990s in the U.S. and might bring about greater declines in the future. Another economist, Rick Nevin, has made the same argument for other nations.

Wow!  Would also seem to lead additional credence to the theory that the lead-lined aqueducts truly did hasten the decline of the Roman empire. One thing I’ve read about lead not mentioned here is that it leads to cognitive impairment, which is definitely also an intermediate cause of more crime.  I remember learning years ago that the discovered that many prisoners had two Y chromosomes, i.e., XYY, and they assumed this let to more crime because these criminals were more aggressive.  Actually turned out that XYY’s were not more aggressive, but much less intelligent than ordinary persons.

If you’re curious, Wilson’s piece also does a nice job summing up other solid explanations for the drop in crime.  Short version: decline of crack/cocaine,  better policing in a variety of ways, and more bad guys in prison where they cannot commit crime (though I suspect all the low-lever marijuana dealers in prison aren’t making us much safer).

About Steve Greene
Professor of Political Science at NC State http://faculty.chass.ncsu.edu/shgreene

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