From 1966 to 2012, the United States of America was host to 31 percent of the mass shootings in the world, despite having only 5 percent of the world’s population.

Research performed by Adam Lankford, associate professor of criminal justice at The University of Alabama, shows that “American exceptionalism, American gun culture and stressors are potential factors in explaining the commonality of public mass shooters in the US,” reports the Times of India.

“Until now, everyone was simply speculating about the relationship between firearms and public mass shootings. My study provides empirical evidence of a positive association between the two,” said Lankford.

The study relied upon an assessment of 171 countries and data from the Federal Bureau of Investigation, among other international sources.

Mass shooting was defined as deaths of four or more people that were not domestic disputes, hostage situations or robberies.

“Public mass shooters in other countries were 3.6 times less likely to have used multiple weapons – typically multiple guns, but occasionally a gun plus another weapon or weapons – than those in the US, where more than half of shooters used at least two weapons,” the study found.

“Given the fact that the US has over 200 million more firearms in circulation than any other country, it’s not surprising that our public mass shooters would be more likely to arm themselves with multiple weapons than foreign offenders,” Lankford said.