The primary focus of our analysis was the systematic review of 18 broad classes of gun policies that have been implemented in some states and the effects of those policies on eight outcomes. We produced research syntheses that describe the quality and findings of the best available scientific evidence. Each synthesis presents and rates the available evidence and describes what conclusions, if any, can be drawn about the policy’s effects on outcomes. In many cases, we were unable to identify any research that met our inclusion criteria (which required a study to provide minimally persuasive evidence for a policy’s effects).

Overall, we found statistically significant evidence that ten of the 18 policies affect four of the main outcomes. For the remaining policies from our analysis, either the policies had inconclusive effects on outcomes or no research about the policies met our inclusion criteria. This does not mean that these policies are ineffective; they might well be quite effective. Instead, it partly reflects shortcomings in the contributions that scientific study can currently offer to policy debates in these areas.

methodology