The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of Gun Policies in the United States (Fourth Edition)

Key Chapter Title List

1. Introduction and Research Methods
2. Policies Regulating the Legal Ownership, Purchase, or Possession of Firearms
3. Policies Regulating Firearm Sales and Transfers
4. Policies Regulating the Legal Use, Storage, or Carrying of Firearms
5. Impact of Minimum Age Requirement Policies
6. Firearm Prohibition Policies Related to Mental Illness
7. Firearm Prohibition Policies Related to Domestic Violence
8. Policies on Firearm Surrender by Prohibited Persons
9. Extreme Risk Protection Order Policies
10. Empirical Effects of Background Check Policies
11. Impact of Waiting Period Policies on Suicide and Homicide
12. Summary of Research Findings and Policy Recommendations

Document Introduction

The formulation of gun policies in the United States has long been constrained by a lack of reliable empirical evidence, making it difficult to balance Second Amendment rights, the public interest in gun ownership, and public health and safety concerns. To address this, the RAND Corporation initiated the Gun Policy in America project in 2016, aiming to provide objective decision-making foundations for policymakers and the public through transparent, unbiased research synthesis. This report, as the fourth edition of the project, represents a significant update and expansion of previous research.

The report focuses on 18 categories of firearm policies that have been implemented in some U.S. states, covering three core areas: regulating firearm owner eligibility, regulating firearm sales and transfer processes, and regulating firearm use and storage behaviors. The research team employed rigorous systematic review methods, screening quasi-experimental studies published between January 1995 and February 2023. They conducted evidence strength ratings and effect analyses centered around eight outcome indicators: suicide, violent crime, unintentional injuries and deaths, mass shootings, police shootings, defensive gun use, hunting and recreation, and the gun industry.

Methodologically, the report established a standardized evidence strength assessment system (no studies, inconclusive evidence, limited evidence, moderate evidence, supportive evidence). It ensured rigorous causal inference through time-series data and control group designs, while also critically examining methodological flaws in the studies. All analyses followed a pre-registered research protocol to ensure transparency and reproducibility of the research process and avoid outcome bias.

Core research findings indicate that strong empirical support has formed for the effects of some policies: Child Access Prevention (CAP) laws effectively reduce firearm suicides, unintentional injuries, and homicides among youth; Stand-Your-Ground laws and Shall-Issue permit laws are associated with increased homicide rates; policies such as background checks and waiting periods have positive effects on reducing suicide and homicide. Simultaneously, the report also points out that research remains extremely scarce in areas like defensive gun use, hunting and recreation, and the gun industry. The long-term impacts and interactive effects of most policies have not yet been fully validated.

The report ultimately proposes two core types of recommendations: first, policy optimization suggestions based on existing evidence, including promoting Child Access Prevention laws, repealing Stand-Your-Ground laws, and strengthening background checks; second, research improvement suggestions targeting evidence gaps, covering aspects such as expanding research funding, improving data collection systems, and optimizing research methodologies. These provide an action framework for building a more robust evidence base for firearm policies.