Executive Summary

A paper on mass public shootings by Adam Lankford (2016) has received massive national and international media attention, getting coverage in the New York Times, the Wall Street Journal, plus hundreds of other news outlets spanning at least 35 different countries. Lankford’s claim was that over the 47 years from 1966 to 2012, an enormous amount of the world’s mass public shooters — 31% — occurred in the United States. Lankford attributed this to America’s gun ownership.

Lankford claims to have “complete” data on such shooters in 171 countries. However, because he has neither identified the cases nor their location nor even a complete description on how he put the cases together, it is impossible to replicate his findings.

It is particularly important that Lankford share his data because of the extreme difficulty in finding mass shooting cases in remote parts of the world going back to 1966. Lack of media coverage could easily lead to under-counting of foreign mass shootings, which would falsely lead to the conclusion that the U.S. has such a large share.

Lankford’s study reported that from 1966 to 2012, there were 90 public mass shooters in the United States and 202 in the rest of world. We find that Lankford’s data represent a gross undercount of foreign attacks. Our list contains 1,448 attacks and at least 3,081 shooters outside the United States over just the last 15 years of the period that Lankford examined. We find at least fifteen times more mass public shooters than Lankford in less than a third the number of years.

Even when we use coding choices that are most charitable to Lankford, his 31 percent estimate of the US’s share of world mass public shooters is cut by over 95 percent. By our count, the US makes up less than 1.43% of the mass public shooters, 2.11% of their murders, and 2.88% of their attacks. All these are much less than the US’s 4.6% share of the world population. Attacks in the US are not only less frequent than other countries, they are also much less deadly on average.

Given the massive U.S. and international media attention Lankford’s work has received, and given the considerable impact his research has had on the debate, it is critical that this issue be resolved. His unwillingness to provide even the most basic information to other researchers raises real concerns about Lankford’s motives.