Philip J. Cook
, Guns in America, 1996, available at
. 2,568 individuals, including 251 gun owners, were surveyed by telephone and asked how they obtained their firearms.
 In the 38 states that have not fully closed the private sale loophole, an estimated 9,856,984 background checks were conducted between
, out of an estimated 16.5 million total firearm transfers in those states. 40 percent of this total—6.6 million transfers—occurred without background checks. Calculation based on FBI data. Available:
, "Effects of State-Level Firearm Seller Accountability Policies on Firearm Trafficking," Journal of Urban Health,
 U.S. Department of Justice, Federal Bureau of Investigation, Supplementary Homicide Reports, 2011.
 Centers for Disease Control and Prevention, National Center for Injury Prevention and Control. Web-based Injury Statistics Query and Reporting System (WISQARS) [online]. (2005) [cited 2012 Dec. 20].
SOURCE Mayors Against Illegal Guns