John R. Lott is, by a significant margin, the most prolific and outspoken researcher on gun-free zones in the United States. He is the author of More Guns, Less Crime and a vociferous opponent of gun laws, having frequently testified before Congress in favor of expanding Right to Carry (RTC) policy. Lott abhors the idea of gun-free zones, and has made the ambitious claim, on numerous occasions, that “with just two exceptions, every public mass shooting in the United States since at least 1950 has taken place where citizens were banned from carrying guns.”
Central to Lott’s argument against gun-free zones is a 2000 study in which he claimed to find that the expansion of RTC laws reduces the number of people in those states killed or injured in multiple-victim shootings by a staggering 78 percent. Lott’s study, however, suffers from enormous flaws, including incorrect statistical modeling and dubious data-selection methodology.
In one example of statistical malpractice, Lott excludes many mass-shooting incidents in which the shooter was committing an additional felony
(such as armed robbery) during the crime, despite the fact that felony-related mass murders account for 36 percent of the data set on which he bases the study
. Lott’s explanation for doing so was an unjustified presumption that bystanders in crimes like robberies or drug deals will already “be engaged in unlawful activities that often require them to carry guns.” However, analysis of this claim reveals that 69 percent of the mass shootings excluded by Lott involved robberies committed in public locations (like convenience stores and fast-food restaurants) where the bystanders were innocent civilians. If RTC laws are to have any effect at all, then surely they would apply to such situations, making it unclear how Lott could choose to ignore them.
When Lott’s research is compared to a more recent study using more appropriate statistical models and a wider range of available data, the beneficial effect of Right to Carry policy vanishes. The authors of a 2002 study, a trio with combined criminology and economics expertise, evaluated RTC laws in 25 states from 1977 to 1999, an expanded version of Lott’s analysis (which covered 23 states in that same time period). They concluded that “RTC laws have no effect on mass public shootings at all.”