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.
“The power of this report should convince academic and medical groups to reevaluate all prior statistical studies of mass shootings and the overall public health danger of firearms,” said Professor Arthur Z Berg, M.D., DLF APA, Harvard University emeritus.
Here is a graph that the New York Times put together using Lankford’s data (data on the rate of mass public shooters by country that has not been released to anyone other than the New York Times) and our graph using the corrected data. While the graph with Lankford’s data shows a positive relationship between the rate of mass public shooters and Small Arms Survey measure of gun ownership (it appears to be driven by the outliers of Yemen and the US), our graph implies a slightly negative relationship. Click on Figures to enlarge.
“Because of faulty research, it is widely believed that a disproportionate share – 31% – of the world’s mass public shooters occurred in the United States,” said Professor Paul Rubin, Samuel Candler Dobbs Professor of Economics, Emory University. “In fact, John Lott’s careful analysis of a very large data set – 437 – pages – shows that the proper number is about 2%, less than the U.S. share of world population. One can only hope that this important research will correct the record.”
Professor Carl Moody, College of William & Mary offered the following: “This is an important paper. The assertion that the US is responsible for 31 percent of worldwide mass shooters is patently absurd. Anyone who doubts the veracity of Dr. Lott’s analysis is welcome to download, for free and in Excel format, the entire Global Terrorism Database (https://www.start.umd.edu/gtd/contact/). There they will find, with a simple back of the envelope calculation, that worldwide since 1970 there have been 58,445 mass firearm attacks. Of these, 402 have occurred in the United States. The US is, according to the GTD. responsible for less than one percent of all mass shootings (0.69 percent) since 1970. Dr. Lott’s calculations are much more carefully done, but Professor Lankford’s analysis is clearly not in the ballpark. Also, social scientists seldom have laboratories. Replication is the only way to verify claims. Any academic who refuses to share his or her data for replication purposes deserves to be shunned.”
This is an amazing response from someone who has refused to provide even the most basic data to other researchers. After reading our study or looking at Appendix 1 listed below, people can judge for themselves the appropriateness of Lankford’s response.
Appendices 1 and 2 for our research on mass public shootings around the world are available here.