The Lead-Crime Hypothesis: When we restrict our analysis to only high-quality studies that address endogeneity the estimated mean effect size is close to zero

The Lead-Crime Hypothesis: A Meta-Analysis. Anthony Higney, Nick Hanley, Mirko Moro. Glasgow Univ. Paper No. 2021 – 02, February 21 2021. https://www.gla.ac.uk/media/Media_774797_smxx.pdf

Abstract: Does lead pollution increase crime? We perform the first meta-analysis of the effect of lead on crime by pooling 529 estimates from 24 studies. We find evidence of publication bias across a range of tests. This publication bias means that the effect of lead is overstated in the literature. We perform over 1 million meta-regression specifications, controlling for this bias, and conditioning on observable between-study heterogeneity. When we restrict our analysis to only high-quality studies that address endogeneity the estimated mean effect size is close to zero. When we use the full sample, the mean effect size is a partial correlation coefficient of 0.11, over ten times larger than the high-quality sample. We calculate a plausible elasticity range of 0.22-0.02 for the full sample and 0.03-0.00 for the high-quality sample. Back-of-envelope calculations suggest that the fall in lead over recent decades is responsible for between 36%-0% of the fall in homicide in the US. Our results suggest lead does not explain the majority of the large fall in crime observed in some countries, and additional explanations are needed.

Keywords: Meta-analysis; Publication selection bias; pollution; lead; crime

JEL: C83, K42, Q53

A view against: Yet another look at that lead-crime meta-study – Kevin Drum