The Staggering Error at the Heart of Pro-Gun Policy

(Photo credit Flickr user Fling93, image has been modified from original)

Devin Hughes

In the aftermath of the Virginia Beach Municipal Center shooting that killed twelve and injured four on May 31st, conservative politicians and pundits pinned the blame for America’s mass shooting epidemic on an old canard: gun-free zones. Republican Representative Thomas Massie of Kentucky recently reintroduced legislation to end gun free zones for schools. While touting his bill, Rep. Massie proclaimed that “98 percent of all mass public shootings in the U.S. since 1950 have occurred in places where the average citizen was banned from possessing guns.”

Rep. Massie is not the first to cite this specific claim on gun-free zones. While speaking at the NRA Convention in 2018, President Trump recited the same statistic: “98 percent of mass public shootings have occurred in places where guns are banned, just so you understand.”

While the 98 percent statistic may appear outlandish and an obscure data point, it is ubiquitously used to justify pro-gun policy ending gun-free zones and is at the heart of pro-gun talking points after a mass shooting. In addition to Rep. Massie’s national bill for example, Republicans have pushed legislation in Arkansas, Missouri, and Wyoming that would largely eliminate gun-free zones. Shockingly, fact-checkers ranging from the Washington Post to Politifact have labeled the 98 percent figure as “Half-True” without delving into the underlying data, giving the statistic a patina of accuracy.

However, closer inspection reveals that a massive data error lies at the heart of the claim that 98 percent of mass shootings occur in gun-free zones.

The 98 percent statistic originates from the work of pro-gun commentator John Lott. Since at least 2014, Lott has claimed that 98 percent or more of mass shootings from 1950 to the present have occurred in gun-free zones, and that mass shooters target such areas because they know they won’t face armed resistance. Therefore, Lott contends, the best way to stop mass shootings is to ensure that civilians are able to carry firearms in as many places as possible.

When pressed to defend his claim, Lott points to his website page that purports to have all the supporting data and evidence, and challenges others to be just as transparent. In one of Lott’s spreadsheets, he claims that since 1950 there were 320 public mass shootings where four or more victims were killed (excluding gang violence, shootings that occurred as a part of a different crime (such as robbery), and incidents in private residences), which are divided into three periods:

7 mass shootings from 1950 to 1976

247 mass shootings from 1977 to 1997

66 mass shootings from 1998 to 2018

As Dr. Louis Klarevas articulates in Johns Hopkins’ online course “Reducing Gun Violence in America: Evidence for Change,” Lott’s claim that there have been 320 public mass shootings with four or more people killed is implausibly large, particularly regarding the 247 purported shootings from 1977–1997. Suspiciously, for this time period Lott only provides “the sums by state and year” for mass shootings, unlike the other two time periods where he provides a detailed list of incidents.

Additional digging reveals that Lott’s entire claim that 98 percent of mass shootings occur in gun-free zones rests on a massive yet basic error: for 1977–1997, Lott counts each individual death in mass shootings as an entire mass shooting.

For example, Lott’s own spreadsheet indicates that there were 14 mass shootings where four or more people died in Oklahoma in 1986. Yet there weren’t 14 mass shootings in Oklahoma that year, just one in which 14 people were killed (excluding the shooter).

Lott’s error, which includes every single mass shooting between 1977 and 1997, completely unravels his claim that only two percent of mass shootings occur in spaces where firearms are allowed as the total number of mass shootings is greatly exaggerated in his data. This makes the percentage of shootings he claims occurred in gun-free zones much larger than it would be without the error. Even accepting all of Lott’s definitions and classifications at face value, his central 98 percent claim is bunk.

Lott’s staggering error in his gun-free zones work is only the latest in a long history of unethical behavior and erroneous statistics. It is long past time media outlets stop providing Lott with a platform as an expert. Any outlets that have published Lott’s falsehood that 98 percent of mass shootings occur in gun-free zones should retract those stories.

UPDATE (8/20/19):
While he made no public announcement, Lott has revised his numbers. Rather than 98 percent of mass shootings being in gun-free zones since 1950 (as seen here), he now claims that 94 percent occurred in GFZs (as seen here) since 1950, and 89 percent since 1998 (as seen here). These numbers do not include the recent shootings in El Paso and Dayton, both of which occurred in areas that allow firearms. Further, Lott’s numbers still contain a significant number of errors, from misclassified shootings such as Umpqua and Hialeah, to not following his own mass shooting definition for cases from 1950–1976. Lott’s 94 percent claim is still wrong, as Louis Klarevas has demonstrated in his research on high-fatality rampage shootings and gun-free zones:

From The Trace:

From Lott’s own spreadsheet, the erroneous data we described:

Lott’s data with error

And the data after his correction (the date in the last row should likely be June 2019, not May 24, 2018):

Lott’s data after correction

Devin Hughes, CFA is the President of GVPedia, a comprehensive resource providing public access to research on gun violence.

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