The Perfect Gun Policy Study in a Not So Perfect Storm

In 2019, Louis Klarevas, Andrew Conner, and David Hemenway published “The Effect of Large-Capacity Magazine Bans on High-Fatality Mass Shootings, 1990–2017.”¹ This seminal study empirically demonstrated that prohibition of large-capacity magazines (LCMs) attenuates mass shooting incidents and lethality.¹ The article ranks in the top 1% of high attention scores and is the most cited and discussed research study in social and legacy media in the history of AJPH. To date, the study has been mentioned in 569 media sources including 73 news outlets (with 87% of the mentions being made by the general public), and there have been 32 research citations.² Dimensions, a research insights platform, reports that the article has received approximately eight times more citations than average.

To that end, we explain why this study continues to have a large impact, leaving an indelible mark in academic circles while garnering the public’s attention despite the political, academic, personal, and cultural hurdles Hemenway has faced dating back to the 1990s.

THE POLITICIZATION OF SCIENCE

Although many topics have been politicized, public health research on gun control was intentionally suppressed by the federal government through the Dickey Amendent.³ The 1996 congressional appropriations bill stipulated that “none of the funds made available for injury prevention and control at the [Centers for Disease Control and Prevention] may be used to advocate or promote gun control.”^3(p549) The political fallout and academic witch hunts, combined with a dearth in funding, were unprecedented.^3–5 A handful of academics, people such as Hemenway, kept the lights on and continued to link policies to gun injury prevention.^3,5 They challenged our thought leaders at a time when there was not enough political will⁶ to reduce gun violence. These academics became icons because they did their research in a hostile environment. They lost research funding, were targeted by the National Rifle Association, and faced daunting congressional inquiries.

Violence researchers either had to remove guns from their research or risked being defunded or attacked by the US Congress and gun rights advocates. Thankfully tenure prevailed, or even the scant public health gun studies would never have happened. The historical context of politicization elevates Klarevas et al. because earlier work, especially that of Hemenway, was published under attack, much like the work of scientists who study climate change, critical race theory, or COVID-19 masking. However, Klarevas and Hemenway have published other research on gun violence that did not rise as high on the public agenda, so we must look to additional factors to understand what catapulted this particular study.

PUBLIC HEALTH IMPLICATIONS OF THE SUPREME COURT RULING

On June 23, 2022, the Supreme Court ruled in favor of the Second Amendment’s operative clause (the right of people to keep and bear arms shall not be infringed) over the prefatory clause (a well-regulated militia being necessary to the security of a free state). The court expanded individual gun rights and threw out several lower court rulings that upheld gun restrictions, including bans on assault-style rifles in Maryland and large-capacity ammunition magazines in New Jersey and California.⁷ In addition, the court limited state policies regarding the purchase, possession, and transportation of firearms and revoked the only gun-control policies known to curtail mass shootings. Thus, the number of mass shootings and their lethality will continue to rise. Ironically, the search for some secret solution to stop mass shootings will redirect policymakers and journalists back to Klarevas et al. yet again after the next mass shooting.

NEWS COVERAGE OF MASS SHOOTINGS

In 2021, nearly 49 000 people in the United States died from guns.⁸ Another 100 000 were shot but survived their injuries. Approximately 60% of gun deaths were suicides, less than 5% were accidental or police shootings, and approximately 36% were homicides. Most homicides are not the result of mass shootings.⁹ In fact, mass shootings make up less than 1% of gun deaths but account for most of the media attention. Suicides are more commonplace events but less likely to make the national news cycles.

The result is that mass shootings more often appear as news stories, thus distorting the public’s perceptions about which types of gun deaths are bigger threats. Parents are more terrified that their children will be killed in a school mass shooting even though there is a much higher likelihood that they will injure or kill themselves if there is an unsecured gun in the home. In the aftermath of a mass shooting, gun violence researchers become part of the media frenzy and are interviewed at length. Because research on mass shootings crosses over from the scientific community to the public, mass shooting research is more likely to capture the general public’s attention.

A BUNCH OF FIRSTS AND SCIENTIFIC RIGOR

First Hemenway and later Klarevas published public health gun research when it was unpopular. More important, they set the stage for gun violence researchers who would come after. Klarevas et al. published their article in 2019, just before the 2020 federal budget included $25 million for the Centers for Disease Control and Prevention and the National Institutes of Health for research on reducing gun-related deaths and injuries after a 24-year hiatus, paving the way for a proliferation of new gun violence research.^10,11

MASS SHOOTING RESEARCHERS DO NOT AGREE ON MUCH

Within academic circles, there is much debate about what constitutes a mass shooting, where it happens, how many people die, and which data to use. Regardless, Klarevas, Conner, and Hemenway followed the public health standard for how to do policy-relevant research. First, they built on existing science on gun violence and mass shootings. Second, they isolated a specific type of mass shooting, one with high lethality (six or more fatalities), and then linked policy to prevention. Gun violence and mass shooting researchers cited this study because the authors used a narrow and specific definition of high lethality, including number of people killed, where the shooting occurred, by whom, the data source, and inclusion and exclusion criteria.¹¹

Even the Federal Bureau of Investigation does not have a mass shooting definition. Instead, it defines “mass murder” as an incident in which four or more people are killed, which can include gun violence. Klarevas et al. employed a sophisticated modeling and research design that was more rigorous than designs used in observational studies. Also, they illustrated the analytic steps they took to rule out alternative interpretations and triangulate their findings, for example examining both state bans and federal bans. They helped build the foundation for future studies while overcoming the limitations of previous research.

MOVING MASS SHOOTING SCIENCE FORWARD

Later research would draw the line in the sand where this study ended or dig into other nuances not addressed.¹¹ For example, Klarevas et al. included both national and state-level bans on LCMs; however, the national legislation and some states also included a ban on assault weapons, so we cannot say with certainty that it was a ban on LCMs, a ban on assault weapons, or a combination. Because assault weapons often (but not always) include LCMs while other guns that are not assault weapons also include LCMs, it is possible that a ban on either would attenuate mass shootings. In addition, although LCM bans were effective, significant loopholes remained that would-be shooters could get around to access illegal weapons and magazines. Most policies grandfathered in individuals who already owned assault weapons with LCMs. Other research would go on to identify stolen guns as pervasive in homicide shootings, so not removing assault weapons and LCMs from the population might reduce the impact of bans.

Moreover, although the weapon bans were applied to gun sales, private vendors were not subject to the bans. After the federal assault weapon ban sunset in 2004, motivated shooters in states with bans were able to easily travel to states without bans, underscoring the need for national policies. Finally, although Klarevas et al. made a good case for including only mass shootings that resulted in six deaths or more, it is important to know whether LCMs empower mass shooters in general, even in the case of shootings with a lower lethality threshold.

SUMMARY

Klarevas, Conner, and Hemenway published an important study that was not popular in select political circles or among gun manufacturers and the National Rifle Association. They firmly established that high-lethality mass shootings can be prevented through policies. Their investigation built on previous mass shooting research, and the gun scholars who came afterward used the study to agree or disagree but always to push the knowledge base forward. Scholars cite this seminal study because of its robustness and quality. Louis Klarevas, Andrew Conner, and David Hemenway are agitators who got into what the late, great Representative John Lewis (D, GA) called “good trouble, necessary trouble.”¹² Scientists walk away from this study knowing that policies can prevent gun deaths, whereas nonacademic citizens have learned that commonsense policies informed by scientific rigor, such as bans on LCMs, help to prevent public massacres. Finally, researchers have learned that they must persevere, sometimes in hostile environments, to inform injury prevention.