Documenting the Iron Pipeline: The flow of guns around America

On Saturday May 2, 2015, Detective 1st Grade Brian Moore of the New York Police Department was shot and killed in while on patrol in Hollis, Queens. Moore’s partner, Eric Jansen, was also shot but was not seriously injured. In the days after the shooting, it emerged that Moore’s killer used a weapon that had been stolen from a gun shop in Perry, Georgia, four years earlier. US Senator Chuck Schumer demanded a “federal crackdown” on illegal interstate gun transfers. Everytown for Gun Safety pointed to the trafficking routes that follow Interstate-95 as a clear culprit. President Barack Obama echoed these concerns. “Guns cross state lines as easily as cars do. If your state has strong gun laws but the neighboring state does not have strong gun laws, the guns come into your state. That’s called the Iron Pipeline.”

New research from Assistant Professor Christopher Morrison and collaborators from around the United States finds evidence that the Iron Pipeline is thriving. The researchers accessed data from the Bureau of Alcohol, Tobacco, Firearms and Explosives that identified the original retail location for all guns used in crimes in 2015-2017 in the contiguous United States. Combining these data from the Boston University State Firearm Laws database, Morrison and colleagues examined associations between the number of guns trafficked between pairs of states and the strength of gun laws at the origin and destination. They found that guns flowed from states with weak laws to states with strong laws, and in particular, from states with weaker buyer laws to states with stronger background check laws.

The figure below is a graph showing flow between all 48 included states. The size of the state node corresponds with the number of gun laws enacted in the states, the thickness of the link indicates the number of guns that flowed from the origin to the destination, and the direction of the flow is clockwise. The figure demonstrates, for example, that flow from Georgia to New York is heavier than flow from New York to Georgia, and that New York has many gun laws while Georgia has few gun laws.

It seems the concerns following Detective 1st Grade Moore’s shooting were well placed. The Iron Pipeline undermines strong state gun laws in New York and elsewhere across the extent of the United States.

The Iron Pipeline: the flow of guns around America

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