Max Fisher and Josh Keller write: Americans make up about 4.4 percent of the global population but own 42 percent of the world’s guns. From 1966 to 2012, 31 percent of the gunmen in mass shootings worldwide were American, according to a 2015 study by Adam Lankford, a professor at the University of Alabama.

Adjusted for population, only Yemen has a higher rate of mass shootings among countries with more than 10 million people — a distinction Mr. Lankford urged to avoid outliers. Yemen has the world’s second-highest rate of gun ownership after the United States.

Worldwide, Mr. Lankford found, a country’s rate of gun ownership correlated with the odds it would experience a mass shooting. This relationship held even when he excluded the United States, indicating that it could not be explained by some other factor particular to his home country. And it held when he controlled for homicide rates, suggesting that mass shootings were better explained by a society’s access to guns than by its baseline level of violence.

If mental health made the difference, then data would show that Americans have more mental health problems than do people in other countries with fewer mass shootings. But the mental health care spending rate in the United States, the number of mental health professionals per capita and the rate of severe mental disorders are all in line with those of other wealthy countries.

A 2015 study estimated that only 4 percent of American gun deaths could be attributed to mental health issues. And Mr. Lankford, in an email, said countries with high suicide rates tended to have low rates of mass shootings — the opposite of what you would expect if mental health problems correlated with mass shootings. [Continue reading…]