The claim that the US has by far the most mass public shootings in the world drives much of the gun-control debate. Many argue that America’s high rate of gun possession explains the high rate of mass shootings.

“The one thing we do know is that we have a pattern now of mass shootings in this country that has no parallel anywhere else in the world,” President Barack Obama warned us. To justify this claim and many other similar quotes, Obama’s administration cited a then-unpublished paper by criminologist Adam Lankford.

Lankford’s claim received coverage in hundreds of news stories all over the world. It still gets regular coverage. Purporting to cover all mass public shootings around the world from 1966 to 2012, Lankford claimed that the United States had 31 percent of public mass shooters despite having less than 5 percent of the population.

But this isn’t nearly correct. The whole episode should provide a cautionary tale of academic malpractice and how evidence is often cherry-picked and not questioned when it fits preconceived ideas.

Lankford’s study reported that over the 47 years there were 90 public mass shooters in the United States and 202 in the rest of world. Lankford hasn’t released his list of shootings or even the number of cases by country or year. We and others, both in academia and the media, have asked Lankford for his list, only to be declined. He has also declined to provide lists of the news sources and languages he used to compile his list of cases.

These omissions are important because Lankford’s entire conclusion would fall apart if he undercounted foreign cases due to lack of news coverage and language barriers.

Lankford cites a 2012 New York Police Department report which he claims is “nearly comprehensive in its coverage of recent decades.” He also says he supplemented the data and followed “the same data collection methodology employed by the NYPD.” But the NYPD report warns that its own researchers “limited [their] Internet searches to English-language sites, creating a strong sampling bias against international incidents,” and thus under-count foreign mass shootings.

Does Lankford’s paper also have that problem?

A new report from the Crime Prevention Research Center, which one of us heads, has just finished collecting cases using the same definition of mass public shootings used by Lankford.

We know of no way to discover most of the cases where four people have been shot to death in an incident in Africa or many other parts of the world during the 1960s, 1970s, 1980s or even 1990s, and that is the reason the new study just looked at the last 15 years from 1998 to 2012 of the 47 years he examined.

Lankford’s data grossly undercount foreign attacks. We found 1,423 attacks outside the United States. Looking at just a third of the time Lankford studied, we still found 15 times as many shooters.

Even when we use coding choices that are most charitable to Lankford, such as excluding any cases of insurgencies or battles over territory, his estimate of the US share of shooters falls from 31 percent to 1.43 percent. It also accounts for 2.1 percent of murders, and 2.88 percent of their attacks. All these are much less than the United States’ 4.6 percent share of the population.

Of the 86 countries where we have identified mass public shootings, the US ranks 56th per capita in its rate of attacks and 61st in mass public shooting murder rate. Norway, Finland, Switzerland and Russia all have at least 45 percent higher rates of murder from mass public shootings than the United States.

When Lankford’s data is revised, the relationship between gun ownership rates and mass public shooters disappears.

How could that be? One possibility is that guns don’t just enable mass shooters; gun owners can also deter and prevent such shootings. Another is that culture — not gun ownership — is a bigger factor in shootings.

The media should be wary of any researchers who fail to let others look at their data. At least on this point, the intellectual base for liberal thunder about mass public shootings is wrong.

John Lott is president of the Crime Prevention Research Center. Michael Weisser was a professor of history at Columbia University.