A recently published study tries to draw a correlation between the sunsetting of the 1994 assault-weapons ban in the United States and an increase in violence in Mexico's border states.
The authors, Arindrajit Dube of the University of Massachusetts, Oeindrila Dube and Omar Garcia-Ponce of New York University, construct a regional argument. They say that after the ban expired in 2004, homicides increased in Mexico's border states where the neighboring U.S. state allowed assault rifles to be sold. Those states are Texas, New Mexico, and Arizona. As a result, homicides in nearby Mexican border states increased by 60 percent, the authors say, compared to Mexican cities hundreds of miles away.
The study carries some plausible data, but weapon-trafficking studies are notoriously underexamined, mostly because the data aren't obtainable. For example, in 2011, the Bureau of Alcohol, Tobacco, Firearms and Explosives found that between 2007 and 2011 in Mexico, 68,000 of 99,000 siezed guns had come from the United States. But the finding that overall, the majority of guns came from the U.S. was not proven -- Mexico didn't let ATF examine all its seized weapons.
Few, if any, experts would argue that gun crime in Mexico is not related to the United States. But quantifying exactly how much of an impact U.S. weapons have had on Mexico is still largely based on estimates. When discussing those numbers, it's useful to note that even the number of Mexico's drug war dead is still not known.
