Frequency of high-fatality mass shootings is rising

A shooter at a bar in Thousand Oaks, California, early yesterday murdered 12 people, including a sheriff’s deputy responding to the incident. It’s the worst shooting incident in the United States in . . . a bit over a week.

There’s an ongoing debate about whether shooting incidents generally are becoming more frequent. The rate of violent crime in the United States has dropped significantly since the late 1980s and early 1990s and, despite some political rhetoric, remains near all-time lows. But there’s little question that the frequency of high-fatality mass shootings — for our purposes, incidents in which at least 10 people are killed — has increased.

MotherJones magazine has tracked mass shootings since 1982, including any incident in which at least four people were killed. From 1984 to 2004, there was an incident in which at least 10 people were killed about once every four years. Over the past four years, there have been eight. There have been four such incidents this year alone.