Synthetic Control Methodology for Examining Firearm Policy.

Purpose of review: Firearm policies have the potential to alleviate the public health burden of firearm violence, yet it is unclear which policies are effective. The current review aims to summarize studies that use synthetic control methods to overcome previous methodological limitations when examining the impacts of firearm policies.

Recent findings: Evidence from studies using synthetic control methods find compelling evidence that purchasing licensing laws for all individuals (e.g., permit-to-purchase) have a preventive effect on firearm deaths. Otherwise, the effects of other firearm policies targeting firearm availability, ownership, sales, and use varied across studies and contexts.

Summary: Synthetic control evaluations find heterogenous effects of firearm policies, suggesting that previous inconsistent findings might reflect their varying impacts across regions rather than methodological limitations alone. Future research should aim to exploit the complementary biases of synthetic control methods to triangulate evidence across evaluation approaches and understand why firearm policies have differential impacts.