BMC Public Health Research article Homicide and geographic access to gun dealers in the United States Douglas J Wiebe*1, Robert T Krafty2, Christopher S Koper3, Michael L Nance4, Michael R Elliott5 and Charles C Branas1 BioMed Central Open Access Address: 1Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia PA, USA, 2Department of Statistics, University of Pittsburgh, Pittsburgh PA, USA, 3Police Executive Research Forum, Washington DC, USA, 4Department of Surgery, The Children's Hospital of Philadelphia, Philadelphia PA, USA and 5Department of Biostatistics, University of Michigan, Ann Arbor MI, USA Email: Douglas J Wiebe* - dwiebe@exchange.upenn.edu; Robert T Krafty - krafty@pitt.edu; Christopher S Koper - ckoper@policeforum.org; Michael L Nance - NANCE@email.chop.edu; Michael R Elliott - mrelliot@umich.edu; Charles C Branas - cbranas@upenn.edu * Corresponding author Published: 23 June 2009 BMC Public Health 2009, 9:199 doi:10.1186/1471-2458-9-199 This article is available from: http://www.biomedcentral.com/1471-2458/9/199 Received: 1 May 2008 Accepted: 23 June 2009 © 2009 Wiebe et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: Firearms are the most commonly used weapon to commit homicide in the U.S. Virtually all firearms enter the public marketplace through a federal firearms licensee (FFL): a store or individual licensed by the federal government to sell firearms. Whether FFLs contribute to gun- related homicide in areas where they are located, in which case FFLs may be a homicide risk factor that can be modified, is not known. Methods: Annual county-level data (1993–1999) on gun homicide rates and rates of FFLs per capita were analyzed using negative binomial regression controlling for socio-demographic characteristics. Models were run to evaluate whether the relation between rates of FFLs and rates of gun homicide varied over the study period and across counties according to their level of urbanism (defined by four groupings, as below). Also, rates of FFLs were compared against FS/S – which is the proportion of suicides committed by firearm and is thought to be a good proxy for firearm availability in a region – to help evaluate how well the FFL variable is serving as a way to proxy firearm availability in each of the county types of interest. Results: In major cities, gun homicide rates were higher where FFLs were more prevalent (rate ratio [RR] = 1.70, 95% CI 1.03–2.81). This association increased (p < 0.01) from 1993 (RR = 1.69) to 1999 (RR = 12.72), due likely to federal reforms that eliminated low-volume dealers, making FFL prevalence a more accurate exposure measure over time. No association was found in small towns. In other cities and in suburbs, gun homicide rates were significantly lower where FFLs were more prevalent, with associations that did not change over the years of the study period. FFL prevalence was correlated strongly (positively) with FS/S in major cities only, suggesting that the findings for how FFL prevalence relates to gun homicide may be valid for the findings pertaining to major cities but not to counties of other types. Conclusion: Modification of FFLs through federal, state, and local regulation may be a feasible intervention to reduce gun homicide in major cities. Page 1 of 10 (page number not for citation purposes)