Today's Tidbit: How Removing Lead from Gasoline Reduces Violent Crime

Before lead was removed from gasoline, lead from car exhaust got into the air, was breathed in by kids, lowered their IQs, and increased crime rates (there is a very strong correlation between IQ and criminal behavior).

Jessica Reyes regressed violent crime rates in all 51 state (including DC) between the years 1985 and 2002 against a number of independent variables.

She found three of significance (at the 5% level):

1. average grams of lead per gallon of gasoline while arrestees were -1 to 3 years of age;
2. whether or not abortion was legal; and
3. beer consumption per capita.

Similar regressions have been performed by others with similar results. The statistical significance results from the fact that between 1975 and 1985 lead was removed from different states at different times.

Reyes estimates that the Clean Air Act resulted in a 56% decrease in violent crime, and that the legalization of abortion resulted in a 29% percent decrease in crime (a result consistent with Levitt and Donohue's in Freakonomics).

From the signs of her coefficients, we can deduce that if you don't like violent crime then lead and beer are bad, while abortion is good (unless, of course, you consider abortion to be a violent crime).

Rick Nevin argues that methyl mercury from coal-fired power plants also damages IQ and leads to more violent crime. China is building one new coal-fired power plant per week. Thank God it's a police state.

References:

• "Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime", 2007 working paper by Jessica Reyes
• "How Lead Exposure Relates to Temporal Changes in {IQ}, Violent Crime, and Unwed Pregnancy", 2000 paper by Rick Nevin
• "Environmental causes of violence", 2010 paper by David Carptenter and Rick Nevin
• Freakonomics 2006 book by Steven Levitt and Stephen Dubner