A much-heralded and widely cited study of 171 countries over nearly a half century purports to show more guns mean more mass shootings, but critics say the report uses bad methodology in a way that rigs the results.

The study by Adam Lankford, a criminal justice professor at the University of Alabama, was published in the journal Violence and Victims in January and has been cited by media outlets -- including The New Yorker, The Washington Post and Time magazine. But the study, formally published earlier this year after a draft was released in academic circles, has raised questions about what critics consider dubious methodology.

“The Lankford ‘study’ is nothing more than junk science disguised as research, and never should have been published in a responsible scholarly journal,” Florida State University criminology professor Gary Kleck told FoxNews.com.

The study, titled “Public Mass Shooters and Firearms: A Cross-National Study of 171 Countries,” concluded that “The United States and other nations with high firearm ownership rates may be particularly susceptible to future public mass shootings, even if they are relatively peaceful or mentally healthy according to other national indicators.”

Academic peers who have sought to examine the findings say Lankford refuses to share the data and details he used to support his findings.

Kleck and others say the obvious hazard in claiming to study 46 years’ worth of shootings in most of the world’s nations is that, while data may be easily found for U.S. shootings, compiling information for developing nations could be all but impossible.

“This would rig results in favor of finding a positive association between gun ownership and mass shootings,” Kleck said.

The reason, Kleck said, is “it would more completely count mass shootings in the U.S., which undoubtedly does have a high gun ownership rate, while yielding artificially low counts of mass shootings in other nations.”

Lankford’s analysis of mass shootings from 171 countries from 1966 to 2012 comes with the caveat “Complete data were available.” In describing his research, Lankford offers only vague hints as to how he identified incidents in poor, non-English-speaking countries going back 50 years.

“I find this claim hard to believe,” Trinity College economics professor Ed Stringham, who has done research using international crime rates, told FoxNews.com.

When asked for his data by FoxNews.com, Lankford declined to provide it. In his study, Lankford says he took NYPD data on mass shootings -- which he acknowledges misses international cases -- and "supplemented [it] with additional data” internationally. Lankford does not say exactly how he collected that additional international data, just noting that it came from searches of “open source” documents and that “all efforts were made to ensure that the same data collection methodology employed by the NYPD was used.”

The NYPD notes that its own researchers “limited [their] Internet searches to English-language sites,” therefore under-counting foreign mass shootings.

FoxNews.com asked Lankford whether he used the same language method as the NYPD, or if he searched using more than just English. Lankford replied that, “my data were not limited to English-language searches." Asked what languages he used in his searches, Lankford declined to provide that information.

“Lankford does not claim to be able to read all the languages used in those 171 nations, or to have made use of others with this ability,” Kleck said. “This method would result in a near-total omission of relevant news stories outside of the English-speaking part of the world.”

Lankford said he may share his methods with fellow scholars at a later date.

"I am open-minded about sharing data with other scholars for collaborative purposes, and consider those opportunities on a case-by-case basis. This is all the assistance I can provide at this time,” Lankford told FoxNews.com by email.

An associate editor of Violence and Victims, which published Lankford’s paper, told FoxNews.com that the journal does not see its role as that of a fact-checker.

“Journal editors generally trust the integrity of authors, and unless reviewers/referrers who are experts in the specific research area call attention to weaknesses in methodology or otherwise challenge findings, the results are not likely to be questioned,” Violence and Victims Associate Editor Edna Erez said.

Editor-in-Chief Roland Maiuro said that Lankford’s paper was approved by anonymous independent researchers.

“The manuscript was subject to blind review by two established researchers with expertise in the area of gun-related violence, critiqued, and revised according to the recommendations made in these reviews,” Maiuro said.

Kleck said a more rigorous and transparent peer review process was in order.

“No qualified scholar would accept work by a researcher who could not, or would not, even explain exactly how he measured his most important variable [mass shootings],” Kleck said.

An expert on transparency said that such data should always be released.

“Any research that seeks to influence the public debate on this topic, as this research clearly does, should be required to make their data available so that other researchers can confirm their findings,” professor Robert Reed, replication editor at the journal Public Finance Review, told FoxNews.com.

The author of this article, Maxim Lott, can be reached on Twitter at @maximlott