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Changes in US mass shooting deaths associated with the 1994–2004 federal assault weapons ban

Analysis of open-source data

DiMaggio, Charles PhD, MPH; Avraham, Jacob MD; Berry, Cherisse MD; Bukur, Marko MD; Feldman, Justin ScD; Klein, Michael MD; Shah, Noor MD; Tandon, Manish MD; Frangos, Spiros MD, MPH

Journal of Trauma and Acute Care Surgery: January 2019 - Volume 86 - Issue 1 - p 11–19
doi: 10.1097/TA.0000000000002060
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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 R2 = 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.

From the Department of Surgery, Division of Trauma and Critical Care Surgery (C.D., J.A., C.B., M.B., J.F., M.K., N.S., M.T., S.F.), New York University School of Medicine, New York, New York.

Address for reprints: Charles DiMaggio, PhD, MPH, Department of Surgery, New York University School of Medicine, 462 First Ave, NBV 15, New York, NY 10016-9196; email:

77th Annual Meeting of AAST and the World Trauma Congress, Sep 26 - 29, 2018, San Diego, California.

© 2019 Lippincott Williams & Wilkins, Inc.