Is the United States an Outlier in Public Mass Shootings? A Comment on Adam Lankford

In 2016 Adam Lankford published a widely propagated article purporting to show that during a 47-year period the United States represented 31 percent of worldwide public mass shooters, and claiming that the outsized U.S. percentage is a result of gun prevalence. We examined the data from 1998 to 2012 and found that, although the U.S. has 4.5 percent of the world’s population, the U.S. represents less than three percent of worldwide mass shooting incidents or mass shooting deaths and less than one percent of mass shooters. What explains this incredible difference? While Lankford claims he is using the conventional definitions of public mass shootings from the FBI and NYPD, it turns out that Lankford’s 31-percent claim is an artifact of his having stripped out much from conventional definitions of ‘public mass shooter,’ notably excluding almost all incidents of terrorism outside the U.S. and most of the cases where more than one shooter is involved. We compare U.S. and non-U.S. public mass shootings using the official definitions from the FBI and NYPD that Lankford claims he is using. We also suggest a reasonable explanation for the fact that, while the U.S. has a relatively large number of lone-wolf shooters compared to the rest of the world, it does not have a relatively large number of public mass shooters.