Additions and Updates to the Gun Policy in America Initiative

Since the March 2018 release of the first edition of The Science of Gun Policy report, there has been a surge in firearm-related scientific research. Through RAND’s Gun Policy in America initiative, and with funding from Arnold Ventures, we have incorporated this expanding body of research into our review of scientific evidence. In 2020, we released an updated review, which added five new classes of gun policies and extended the period over which we conducted our literature search to the period from 1995 to 2018. A third edition updated our findings and conclusions with research published through October 2020. This fourth edition updates our findings and conclusions with research published through February 2023.

Here, we describe the major updates and changes to the Gun Policy in America website and research reviews since our last major update in 2023.

Expanded and Updated Review of the Scientific Evidence on the Effects of Gun Policies

This fourth edition of our review of available evidence was released in 2024, and uses unchanged inclusion criteria for reports estimating the effects of the following 18 classes of gun policies on eight outcomes:

After reviewing thousands of candidate studies, we identified 182 that met our inclusion criteria, nearly three times the number of included studies in our original review (63), and an increase of 30 studies since our 2023 review.

• 1997: 3
• 1998: 8
• 1999: 3
• 2000: 3
• 2001: 10
• 2002: 5
• 2003: 9
• 2004: 5
• 2005: 4
• 2006: 2
• 2007: 3
• 2008: 4
• 2009: 5
• 2010: 4
• 2011: 2
• 2012: 2
• 2013: 4
• 2014: 7
• 2015: 7
• 2016: 7
• 2017: 9
• 2018: 17
• 2019: 11
• 2020: 18
• 2021: 9
• 2022: 16
• 2023: 4

Note: Study data for 2023 are incomplete.

Updated Conclusions

In our research synthesis, we analyze the available evidence for how each of the 18 policies affects eight outcomes (e.g., mass shootings) and provide our judgment of the strength of that evidence, using the following evidence ratings: inconclusive, limited, moderate, or supportive. (Read more about how these ratings are defined in What Science Tells Us About the Effects of Gun Policies.) While our criteria for summary judgments are unchanged from the last edition, we revised our approach to assessing the methodological quality of individual study estimates to formalize certain criteria related to potential confounding and measurement issues. Our updated conclusions thus reflect both revisions to our quality assessment criteria as well as the newly published literature.

For one of the policies that we examined in our 2023 review, the newly included literature increased the strength of available evidence above the previous rating to supportive, our highest evidence rating. Specifically, there is now:

• Supportive evidence that minimum age requirements for purchasing a firearm reduce firearm suicides among young people. In our last review we concluded evidence for this relationship was moderate.

For two other policies, the newly included literature increased the strength of available evidence above the previous rating to supportive, our highest evidence rating, for a broader set of outcomes. Specifically, there is now:

• Supportive evidence that stand-your-ground laws increase total homicide and firearm homicide rates. In our last review, we concluded evidence for the relationship with firearm homicide was moderate.
• Supportive evidence that more permissive concealed-carry laws increase total homicide, firearm homicide, and overall violent crime. In our last review, we concluded there was limited evidence for the relationship with overall violent crime.

Five other policies now have limited evidence ratings that in 2023 were considered inconclusive, or for which no studies met our inclusion requirements. Specifically, there is now:

• Limited evidence that minimum age requirements for possessing a firearm may decrease total suicides among young adults.
• Limited evidence that extreme-risk protection orders reduce total and firearm suicides.
• Limited evidence that licensing and permitting requirements may decrease mass shootings.
• Limited evidence that firearm prohibitions for individuals convicted of domestic violence misdemeanors may decrease firearm-related intimate partner homicides.
• Limited evidence that permitless-carry laws increase fatal police shootings.

In several other cases, we have been able to change the status of evidence on policy effects from “no studies met our inclusion requirements” to “inconclusive.” In these cases, studies are now available that examine the policy effects, but their findings do not support a conclusion about the likely effects of the policy.