Statistical Methods to Estimate the Impact of Gun Policy on Gun Violence

Gun violence is a critical public health and safety concern in the United States. There is considerable variability in policy proposals meant to curb gun violence, ranging from increasing gun availability to deter potential assailants (e.g., concealed carry laws or arming school teachers) to restricting access to firearms (e.g., universal background checks or banning assault weapons). Many studies quantify policy impacts on gun violence using methods that combine state-level variation in the enactment of these policies with repeated measurements of the outcome of interest both before and after the policy change. In this chapter, we highlight the key features of the design and analysis of such evaluations, along with the associated opportunities and challenges, especially for studying gun policies in particular. We focus primarily on difference-in-differences and synthetic controls methods when there is staggered adoption of policies across jurisdictions, estimating the impacts of right-to-carry laws on violent crime as a case study.