How Much Did Lead Contribute to Mass Incarceration? Cont'd

Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.

Responding to our request for more evidence related to the lead/crime connection, a reader points to economist Rick Nevin, one of the leading researchers investigating that connection. Nevin wrote as recently as last month about how different cohorts were affected by lead:

The crime decline in recent years has been slower than the earlier decline in blood lead because steep arrest rate declines for youths have been partially offset by rising arrest rates for older adults. … This shift in arrest rates shows ongoing massive declines for youths born across decades of declining lead exposure, smaller arrest rate declines for adults born in the early years of the lead exposure decline, and increasing arrest rates for older adults born when lead exposure was increasing.

The shift in arrest rates has caused a corresponding shift in prison incarceration. From 2001 to 2013, incarceration rates fell by 59% for males ages 18-19 and 30% for males in their 20s, but increased 33% for men ages 40-44 and surged 86% for men ages 45-54. Proponents of “tough-on-crime” sentencing credit prison incapacitation for much of the USA crime decline – “when a criminal is locked up, he’s not ransacking your house” – but the largest arrest rate declines have occurred among younger age groups with large contemporaneous incarceration rate declines. ... Mendel reports that lead exposure can explain juvenile justice trends that cannot be explained by reform efforts or other crime theories.

Mark Kleiman, on the other hand, voiced skepticism on the lead/crime connection in response to Kevin Drum’s widely lauded 2013 essay, invoking the work of economist Philip J. Cook and criminologist John Laub. Another skeptic at the time was Ronald Bailey:

Interestingly, in a 2012 working paper [Rick] Nevin argues that the increase in IQs in the early part of the 20th century resulted from lessened exposure to lead paint and that increases in the average IQ scores slowed down as tetra-ethyl lead exposure from gasoline rose. Perhaps Nevin would argue that the increase in the U.S murder rate from 1.2 per 100,000 in 1900 to 9.7 per 100,000 in 1933 can be attributed to rising lead paint exposure?

Drum is right that exposure to lead increases the chances that a person will suffer the sorts of neurological damage that lowers their intelligence and lower intelligence is well-known to correlate with increased criminality. Reducing such exposures has no doubt contributed to our happily falling crime rates. But it is likely that other factors including more policing, more incarceration, less crack, increased concealed carry, and other such efforts to control crime have contributed as well.

Steven Novella is on the same page:

The real question, it seems to me, is the magnitude of this [lead] effect, especially compared to other effects on crime. The Mother Jones article, by Kevin Drum, cited a figure that 90% of the increase in crime since WWII might be due to lead. He was called out on this figure by blogger Deborah Blum, and Drum later printed a correction. He said the 90% figure is at the upper limit of the range of estimates, and that 50% is likely closer to the truth.

In the review I cited above, reference is made to research showing that “as much as 20%” of crime is “lead related.” One small point – Drum’s now 50% figure, as he points out, is the rise in crime, not the cause of all crime. The 20% figure cited in research is all crime – so these numbers may be compatible. Either way, the 90% figure likely overstates the connection.

Therefore, even accepting the 20% figure, that means 80% of crime has nothing to do (at least directly) with lead, and the sociologists are free to continue to speculate and study about the myriad of social causes of crime.

Caty addressed those causes in a note last night.