Mass shooters in America disproportionately target workplaces and schools, while shooters outside the U.S. largely attack military facilities, a new study finds. The study’s author attributes the discrepancy to a distinctly “American strain” that causes this country’s mass shooters to interpret the everyday stresses of professional and educational environments in the U.S. as equivalent to the life-and-death conflicts of combat zones.

“The strains you experience can be shaped by your culture, but also shaped by your own mind and a complete lack of perspective,” Adam Lankford, study author and professor at the University of Alabama, tells The Trace. “Even when these mass shooters end up killing random strangers, these victims typically represent the social systems that the offenders believe mistreated them in unforgivable ways.”

The research, presented last weekend at the annual meeting of the American Sociological Association, looks at public mass shooters in 171 countries across the globe between 1966 and 2012. The United States was home to 90 public mass shooters in that period, or 31 percent of the world’s total. The Philippines were second, with 18. Only four countries studied had more than 10. When the analysis is narrowed to schools and workplace settings, America claims 62 percent of the world’s public mass shooters. Shooters in the U.S. also targeted public businesses, restaurants, and theaters at a higher rate than any other country.

The findings lead Lankford to believe that workplaces and schools are sites of more public mass shootings due to “the social pressure to achieve the American Dream but a lack of means to do so,” or what he calls “American strain.” Lankford points to the Virginia Tech and Aurora shootings, which were both perpetrated by college students, as examples of how the stresses of school and frustrated ambition can manifest in violent ways when coupled with mental illness.

“Despite being in no physical danger and having the freedom to make real changes to their lives, many of the American students and workers similarly felt like they were trapped prisoners, and that becoming highly successful was a matter of life-and-death,” the study reads. “One frightening possibility is that this dangerously self-centered myopia is particularly symptomatic of American exceptionalism itself.”

The research uses data from the New York City Police Department’s 2012 active shooter report and the FBI’s 2014 active shooter report. All incidents considered in Lankford’s study included the death of a bystander, and were not solely domestic or gang-related. Drive-by shootings, hostage-taking incidents, and robberies were also not included. All but one of the shooters were male, and their ages ranged from 15 to 66, with a mean age of 32. The average shooter studied killed eight victims, and more than half died as a direct result of their attack.

[Photo: Flickr user Via Tsuji]