Where Are the Guns? Evaluating Gun Prevalence Measures and Their Connection with Homicides Using Gun Sales Data

One of the most controversial elements of research in gun violence is the debate surrounding which proxy for gun prevalence best captures the true variation in gun availability. We test the effectiveness of several common gun prevalence proxy variables against what is arguably the best measure of changes in gun availability: firearm sales. Utilizing a comprehensive list of gun sales by county in the state of Pennsylvania, we make several observations: First, gun sales are positively correlated with federal firearm licenses (gun dealers) per mile. Second gun sales are negatively correlated with federal firearm licenses per capita, and the proportion of gun suicides to total suicides. Third, we replicate the results of Johnson and Robinson (2021) using gun sales. We find increases in handgun sales are positively correlated with gun homicides. Long-gun sales are negatively correlated with homicide. Last, we discuss the limitations of using legal gun sales as a gun prevalence measure in a more general context, as it fails to consider the migration of guns. Consequently, we advise researchers to use gun dealers as a measure of gun prevalence and specifically in a way that considers markets bleeding over arbitrary lines. Using an accurate measure of gun prevalence is paramount when assessing the efficacy of policy