State Gun Law Grades and Impact on Mass Shooting Event Incidence: An 8-Year Analysis

Abstract

BACKGROUND: 

Gun violence, particularly in the form of mass shooting events (MSE), is a growing, significant public health crisis in the US. Whether stricter gun laws decrease MSE is not known. We hypothesized that stronger state gun laws would be associated with lower MSE incidence.

STUDY DESIGN: 

Mass shooting events, defined as at least 4 people injured in a single event, and state gun law grade data for years 2014 through 2021 were obtained from the Gun Violence Archive and Giffords Law Center, respectively. An A grade indicated strictest gun control laws, and F indicated the weakest. US 2020 Census data were used to estimate MSE per million per state. The number of MSE per million was examined for association with gun law grades.

RESULTS: 

From 2014 through 2020, there were a total of 2,736 recorded MSE, with at least a 2-fold increase in incidence from 272 in 2014 to 626 in 2020. Concomitantly, the number of F grade states decreased from 27 to 21 (22%). The MSE mean (SD) per F state increased from 4.0 (5.1) in 2014 to 9.7 (10.3) in 2020 (p = 0.03). No differences were found in unadjusted number of MSE per year by gun law grade for any study year examined (p = 0.67). After adjusting for population, this finding of no difference persisted.

CONCLUSIONS: 

Strength of state gun law grades does not affect MSE incidence, even after correction for population size. This suggests that legislation by itself is not an effective prevention measure and other broader and meaningful primary gun violence interventions are needed.

In Brief

Over the previous 7 years, the incidence of non-fatal mass shooting events (MSE) increased 2.3-fold in 2020 despite concomitant increases in the strength of state gun law grades. MSE mortality rate decreased with increasing state gun law grades, ranging from 4.6% to 8.8% in Grade A and F states, respectively.