Changes in US Mass Shooting Deaths Associated With the 1994-2004 Federal Assault Weapon Ban: Analysis of Open-Source Data

Background A federal assault weapons ban has been proposed as a way to reduce mass shootings in the U.S. (U.S). The Federal Assault Weapons Ban (A.W.B.) of 1994 made the manufacture and civilian use of a defined set of automatic and semi-automatic 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 U.S. population. We compared the 1994-2004 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% CI 82.8, 88.9) in 44 mass-shooting incidents. Mass shootings in the U.S. 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-squared = 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% CI 0.22,0.39). Conclusions Mass-shooting related homicides in the U.S. were reduced during the years of the federal assault weapons ban of 1994 to 2004. Study Type Observational Level of Evidence III/IV 77th Annual Meeting of AAST and 4th World Trauma Congress Sep 26 - 29, 2018 San Diego, California Corresponding Author: Charles DiMaggio, PhD, MPH, Professor of Surgery and Population Health, Director of Injury Research, Department of Surgery, New York University School of Medicine, 462 First Avenue, NBV 15, New York, NY 10016-9196, Charles.DiMaggio@nyumc.org, Office: 212.263.3202, Mobile: 516.308.6426 Funding Statement: There are no federal or non-federal funding sources associated with this study. Conflict of Interest Statement: The authors have no conflicts of interest to declare. © 2018 Lippincott Williams & Wilkins, Inc.

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