Changes in US mass shooting deaths associated with the 1994-2004 federal assault weapons ban: Analysis of open-source data

J Trauma Acute Care Surg. 2019 Jan;86(1):11-19. doi: 10.1097/TA.0000000000002060.

Abstract

Background: A federal assault weapons ban has been proposed as a way to reduce mass shootings in the United States. The Federal Assault Weapons Ban of 1994 made the manufacture and civilian use of a defined set of automatic and semiautomatic weapons and large capacity magazines illegal. The ban expired in 2004. The period from 1994 to 2004 serves as a single-arm pre-post observational study to assess the effectiveness of this policy intervention.

Methods: Mass shooting data for 1981 to 2017 were obtained from three well-documented, referenced, and open-source sets of data, based on media reports. We calculated the yearly rates of mass shooting fatalities as a proportion of total firearm homicide deaths and per US population. We compared the 1994 to 2004 federal ban period to non-ban periods, using simple linear regression models for rates and a Poison model for counts with a year variable to control for trend. The relative effects of the ban period were estimated with odds ratios.

Results: Assault rifles accounted for 430 or 85.8% of the total 501 mass-shooting fatalities reported (95% confidence interval, 82.8-88.9) in 44 mass-shooting incidents. Mass shootings in the United States accounted for an increasing proportion of all firearm-related homicides (coefficient for year, 0.7; p = 0.0003), with increment in year alone capturing over a third of the overall variance in the data (adjusted R = 0.3). In a linear regression model controlling for yearly trend, the federal ban period was associated with a statistically significant 9 fewer mass shooting related deaths per 10,000 firearm homicides (p = 0.03). Mass-shooting fatalities were 70% less likely to occur during the federal ban period (relative rate, 0.30; 95% confidence interval, 0.22-0.39).

Conclusion: Mass-shooting related homicides in the United States were reduced during the years of the federal assault weapons ban of 1994 to 2004.

Level of evidence: Observational, level II/IV.

Publication types

  • Comparative Study

MeSH terms

  • Firearms / legislation & jurisprudence*
  • Firearms / statistics & numerical data
  • Homicide / statistics & numerical data*
  • Homicide / trends
  • Humans
  • Industry / legislation & jurisprudence*
  • Mortality / trends
  • Observational Studies as Topic
  • Suicide / statistics & numerical data
  • Suicide / trends
  • United States / epidemiology
  • Wounds, Gunshot / epidemiology*
  • Wounds, Gunshot / mortality
  • Wounds, Gunshot / prevention & control