Evaluating Methods to Estimate the Effect of State Laws on Firearm Deaths

The RAND Corporation launched its Gun Policy in America initiative with the goal of creating objective, factual resources for policymakers and the public on the effects of gun laws. As a part of this project, RAND researchers conducted a systematic literature review and evaluation of scientific studies on the effects of 13 classes of policies. One of the findings of the review was that the effects of policies estimated in the literature appeared to be sensitive to the specific statistical methods that were employed. This suggests the importance of identifying the most-appropriate statistical methods to use on these data. In this report, the authors use simulations to assess the performance of a wide range of statistical models commonly used in the gun policy literature to estimate the effects of state-level gun policies on firearm deaths. The study aimed to identify the most-appropriate statistical modeling and analysis methods for estimating the effect of these policies on firearm deaths, which may help in the evaluation of whether estimates from prior research can be considered to be accurate. The results suggest substantial statistical problems with many of the methods used. The authors also identify the best method among those assessed. This report should be of interest to researchers familiar with statistical methods for estimating causal effects in longitudinal time series data, those who are trying to understand the effects of gun policies as revealed in the existing literature, or those who are planning new studies that use statistical models to investigate these effects.