Before we dive in, there are two important caveats: There’s no agreed-upon definition of “mass shooting,” and “gun-free zone” is subject to interpretation. As we’ve reported, in the 1980s, the FBI established a definition for “mass murder” as “four or more victims slain, in one event, in one location.” Shooters are not included in the victim count if they committed suicide or were killed in a justifiable homicide, according to a Congressional Research Service report. But “mass murder” is not the same as “mass shooting.”
The lack of consistency of definitions has led researchers to draw wildly different conclusions and has added ambiguity to something that, on face value, should be simple enough to determine. As with all statistics, it depends on how you count. Let’s dig in.
Trump is citing an updated 2014 report from the Crime Prevention Research Center.
Founded by economist John R. Lott, CPRC is cited regularly by gun-rights advocates. Lott found that 98.4 percent of mass shootings occurred in gun-free zones between 1950 and July 10, 2016. Some quick Googling turned up another study — from the gun-control advocacy group Everytown for Gun Safety — that found that 10 percent of mass shootings between 2009 and 2016 took place in gun-free zones.
Using data that Lott provided, we tightened the time frame so we could compare his research with the Everytown study. Under Lott’s methodology, we found that about 86 percent of mass public shootings took place in gun-free zones from 2009 to 2016.
Eight-six percent and 10 percent are about as far apart as statistics get. So who’s right? The answer hinges on dueling definitions. For the sake of an apples-to-apples comparison, let’s break down how Lott and Everytown calculated the percent of mass shootings in gun-free zones between 2009 and 2016.
What is a ‘mass shooting’?
Everytown identified 156 mass shootings between 2009 to 2016. Lott found 28 mass public shootings over the same period. Both Lott and Everytown define a mass shooting as any incident in which “four or more” people are killed in one location, not including the shooter.
Here’s where the two start to differ. Lott tightens his definition, excluding shootings that resulted from gang or drug violence or during the commission of a crime. Everytown includes these incidents. Lott justifies this by citing a 2014 FBI study on active-shooter incidents. (Caveat: An active shooter may be but is not necessarily the same as a mass shooter. The FBI did not require fatalities when it evaluated “active shooter” situations, and the report underlines this difference, noting, “This is not a study of mass killings or mass shootings, but rather a study of a specific type of shooting situation law enforcement and the public may face.”)
Another major difference between Lott and Everytown is in where they argue a mass shooting can occur. Lott is very clear that he looks only at “mass public shootings.” Referring to the same FBI study, he writes, “The FBI also defines ‘public’ places as ‘includ[ing] commercial areas (divided into malls, businesses open to pedestrian traffic, and businesses closed to pedestrian traffic), educational environments (divided into schools [pre-kindergarten through 12th grade] and IHEs), open spaces, government properties (divided into military and other government properties), houses of worship, and health care facilities.’ ”
Lott did not mention that the list, defined as locations “where the public was most at risk during an [active-shooter] incident,” also included “residences,” which accounted for 4.4 percent of such incidents. He explained these exclusions in a Fox News op-ed, arguing that “mass public shootings are uniquely motivated,” unlike a shooting that is the result of a gang fight or a drug sale. He added that “shootings in private residences are distinctly different, since they often involve killers who know the homeowners and whether they own guns.”
Louis Klarevas, a University of Massachusetts professor and the author of “Rampage Nation: Securing America from Mass Shootings,” dismissed Lott’s reasoning, noting that plenty of mass shootings occurred in residential settings and querying why those victims should be overlooked. Everytown’s director of research and implementation, Sarah Tofte, went further. “The claim that so-called ‘gun-free zones’ attract mass shooters doesn’t stand up to scrutiny,” she told us via email. “It’s just not what the numbers show. We look closely at the data on mass shootings, and it shows that relatively few take place in areas where civilians are prohibited from carrying firearms. In fact, the vast majority of mass shootings take place in private homes and are often tied to domestic violence.” The organization’s data found that incidents that took place in private homes accounted for 63 percent of the total number of mass shootings they examined between 2009 and 2016.
What is a ‘gun-free zone’?
It’s not only the discrepancies between how Lott and Everytown define “mass shooting” that contribute to their differing estimates — there is also disagreement about how to define “gun-free zone.”
Everytown reported 16 mass shootings in gun-free zones between 2009 and 2016; Lott reported 24. This is clearly attributed to the difference in definitions. Everytown defines gun-free zones as “areas where civilians are prohibited from carrying firearms and there is not a regular armed law enforcement presence.”
Here, Lott has a much wider definition. In an email, he wrote that gun-free zones are “places where only police or military policy are classified, places where it is illegal to carry a permitted concealed handgun, places that are posted as not allowing a permitted concealed handgun, places where ‘general citizens’ are not allowed to obtain permits or where permits are either not issued to any general citizens or to only a very tiny selective segment.”
In layman’s terms, Lott’s definition is so wide that the White House, where there are snipers on the roof, would be considered a gun-free zone. His data set classifies the shootings that took place at Fort Hood and the Washington Navy Yard as having occurred in gun-free zones. Klarevas disputed Lott’s characterization — wondering how “a place can be a gun free zone if guns are present?”
Lott previously defended his assessment. “Regular military members are banned from carrying guns at military bases in the United States, making the bases surprisingly soft targets,” he wrote. “The only people who can carry guns on domestic bases are military police, so the situation is much the same as at the Pulse nightclub.”
A White House official stood by Lott’s study, saying the president had cited a widely used statistic.
Lott’s original data set — which Trump referenced — spans from 1950 to 2016, but the admittedly vague concept of “gun-free zones” entered the lexicon only in the early 1990s, when two federal laws that restrict guns in and around schools were passed. Before 1990, Klarevas said, only certain government facilities (post offices, for example) explicitly prohibited firearms.
So where did the prior 40 years of data come from? Lott used a wide definition of “gun-free zone” to compile this data. He said he included anyplace where a “general citizen” wasn’t able to carry a concealed weapon. This included any state that didn’t have either a right-to-carry or concealed-carry law.
No matter how we spin these numbers, one thing is clear – they can be spun. And they have been. Without a commonly accepted and uniform definition of “mass shooting” or agreement on what constitutes a “gun-free zone,” it’s difficult to settle this debate. Advocates on both sides can point to holes and debatable logic in the reasoning of the study from the other sides.
But Lott’s study is really not our focal point today. It’s the president. As always, the burden for proving the accuracy of a claim is on the speaker. When the gap between dueling studies is so large, largely because the count depends on definitions, politicians need to be especially careful about citing one. Trump lunged for a dramatic statistic without including necessary context. He earns Two Pinocchios.
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