Are Lax US Gun Laws Spilling Violence into Mexico?

The question:

Do more guns cause more violence?

The experiment:

We exploit a natural experiment induced by the 2004 expiration of the U.S. federal assault weapons ban to examine how the subsequent exogenous increase in gun supply affected violence in Mexico. The expiration relaxed the permissiveness of gun sales in border states such as Texas and Arizona, but not California, which retained a pre-existing state-level ban.

The results:

Using data from mortality statistics and criminal prosecutions over 2002-2006, we show that homicides, gun-related homicides and gun-related crimes increased differentially in Mexican municipios located closer to Texas and Arizona ports of entry, relative to those nearer California ports.

Our estimates suggest that the U.S. policy change caused at least 158 additional deaths each year in the post-2004 period. Gun seizures also increase differentially, and solely for the gun category that includes assault weapons. The results are robust to controls for drug trafficking, policing, unauthorized immigration, and economic conditions in U.S. border ports, as well as drug interdiction efforts, trends by income and education, and military and legal enforcement efforts in Mexican municipios.

The conclusion:

Our findings suggest that U.S. gun laws have exerted an unanticipated spillover on gun supply in Mexico, and this increase in gun supply has contributed to rising violence south of the border.

From a paper presented by Oeindrila Dube at NYU’s Development Seminar, with Arindrajit Dube and Omar Garcia-Ponce.