Understanding the Interstate Export of Crime Guns: A Gravity Model Approach

I. INTRODUCTION In 2009, according to U.S. government statistics, there was a total of 1,318,398 violent crimes committed nationwide, or about 429.4 violent crimes per 100,000 people. (1) Of these violent crimes firearms were used in approximately 67.1% of murders, 42.6% of robberies, and 20.9% of aggravated assaults. In cases where guns are recovered from crime scenes the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) attempts to trace the gun to determine its origin. According to data from 2009, of the 238,107 guns recovered from crime scenes, the ATF was able to successfully trace 145,321 (61%) of these guns. Based on these traces the ATF was able to determine that 43,254 of these crime guns (30%) were originally sold in a different state from which they were recovered. (2) The top three states which were net exporters of crime guns (and the number of net exports) were: Virginia (1,573), Indiana (1,351), and Mississippi (1,199). The top three net importers (and number of net imports) were: New York (3,090), Illinois (2,799), and California (2,690). What may explain why some states tend to be net exporters of illegal guns and others net importers? The goal of this article is to offer an answer to that question. To explain the movement of crime guns across state lines this article borrows the well-known gravity model from the international trade literature and applies it to interstate movement of crime guns. Results from the estimated gravity model show that the typical factors that explain the movement of goods between nations (e.g., market sizes and the distance between them) also explain the movement of traced crime guns between states. The empirical results also show that differences in the presence of gangs among states partly explain the movement of traced crime guns between states. Finally, the regression results show that differences in state laws affecting gun ownership and sales are important in explaining the movement of traced crime guns across state lines. For example, one of the robust findings is that states with laws that require owners to report lost or stolen guns tend to export fewer illegal guns to other states. This latter result is of particular interest as it demonstrates an externality or "spillover" effect of differential gun control laws on the flow of illegal guns where states with weak gun control laws tend to export guns to states with stricter laws. The remainder of this article is organized as follows. Section II provides an overview of the market for illegal guns and federal and state gun laws enacted to control the purchase and sale of guns. Section III develops the model used to estimate the movement of crime guns across states. Section IV contains a description of the estimation approach and the empirical results. Section V contains concluding remarks. II. GUN LAWS AND SOURCES OF ILLEGAL GUNS There are an estimated 250 million guns in circulation in the United States. (3) Laws affecting the purchase and sale of firearms are in place at both the federal and state levels. (4) At the federal level one of the most important laws is the 1968 Gun Control Act (GCA) that requires firearms dealers to hold a federal firearms license (FFL) and prohibits certain individuals from purchasing or owning guns (e.g., convicted felons, illegal drug users, illegal aliens, individuals convicted for domestic violence). In addition, the GCA limits the interstate transfer of guns to only those holding an FFL. The next major federal gun law came 25 years later when the Brady Handgun Violence Protection Act was passed by Congress in 1993. This law requires that licensed dealers conduct a background check of potential purchasers to ensure they are eligible to buy a gun. How do legal guns become illegal guns'? Cook et al. (2007) notes that the transmission of guns to individuals who are prohibited from owning them generally occurs in three ways. …