In this report, part of the RAND Corporation's Gun Policy in America initiative, researchers seek objective information about what the scientific literature reveals about the likely effects of various gun laws. In this second edition of an earlier work, the authors add five gun policies to the 13 examined in the original analysis and expand the study time frame to incorporate a larger body of research. With those adjustments, the authors synthesize the available scientific data on the effects of 18 policies on firearm deaths, violent crime, the gun industry, defensive gun use, and other outcomes. By highlighting where scientific evidence is accumulating, the authors hope to build consensus around a shared set of facts that have been established through a transparent, nonpartisan, and impartial review process. In so doing, they also illuminate areas where more and better information could make important contributions to establishing fair and effective gun policies.