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Access to Assault Weapons Amplifies Pre-existing Risks of Violence

- December 18, 2012

The following is a guest post by New York University political scientist Oeindrila Dube.


On October 23rd, 2010, gunmen mowed down 14 youth and injured 12 others at a teenager’s birthday party in Ciudad Juárez, Mexico. How is this related to Friday’s tragic killings at Sandy Hook Elementary School? First, both involved the use of semi-automatic weapons bought in the United States. Three of the guns in the Juárez killings came from the U.S. through its failed gun-tracking program, Operation Fast and Furious.  Second, both show how access to military-style guns can escalate homicides in volatile contexts where there is some underlying demand for these lethal weapons.

My recent working paper  (“Cross-Border Spillover: U.S. Gun Laws and Violence in Mexico”) with Arindrajit Dube and Omar García-Ponce directly examines this idea.  Yesterday, Eric Voeten summarized one finding from an earlier version of the paper: the 2004 expiration of the U.S. Federal Assault Weapons Ban (FAWB) fuelled more killings and gun seizures in Mexican municipios located closer to the states that started selling these weapons –Texas, Arizona and New Mexico. The rise in gun-related killings accounted for about 30% of such murders in the two years after the ban was lifted.

We also find that not all areas were affected equally: the FAWB expiration led to much larger homicide spikes in areas that were unstable in the context of the Mexican drug war.  Informal agreements between drug cartels and local politicians disintegrated as a result of Mexico’s democratic transition, creating cartel destabilization as a by-product in some areas.  Consistent with this account, we detect much larger homicide increases in municipios that were more electorally competitive prior to 2004. And, these effects were larger still in high nacro-trafficking areas.

The general lesson is that access to arms amplifies underlying risk factors in translating guns into violence.  We can draw on this lesson for understanding the gun-crime relationship in a variety of contexts.  What changes is simply the relevant risk factor. It may be cartel instability in Mexico; another possibility is mental health related instability within a given American community, where the presence of high-powered weapons translates a disturbed individual into a killing spree.  Other communities may be at risk due to economic downturns, or the existence of gangs, etc…

Social science research has the capacity to identify some of these factors, and partly predict where military-style weapons are likely to exert the greatest damage.  But predicting whether guns will trigger killings remains a gamble, and an especially uncertain one for communities with un-diagnosed risks.

Greater gun control is one means of eliminating this gamble. The results in our paper directly imply that re-instatement of the assault weapons ban will help curb criminal homicides south of the border.  (After all, 90% of the crime guns seized in Mexico are traced back to the U.S., according to a 2009 GAO report .) But the general lesson distilled also suggests that these restrictions are likely to reduce tragic shootouts among the most vulnerable communities closer to home as well.