It isn't.

Posted on: February 22, 2018 at 13:45:09 CT

http://www.slate.com/articles/news_and_politics/politics/2017/10/what_the_white_mass_shooter_myth_gets_right_and_wrong_about_killers_demographics.html

In this bigger data set, the proportion of white mass shooters drops down to 56 percent, by my count. Judging by those newer numbers, and the most current census estimate that 76.9 percent of Americans are white, the whites-are-overrepresented-among-mass-shooters meme appears even less accurate. Perpetrators that Mother Jones classifies as Asian make up 7.4 percent of the data set, versus an estimated 5.7 percent of the population, while those MoJo identifies as black represent 17.0 percent of the mass shooters in the database versus an estimated 13.3 percent of the population. According to this data set, then, Asians and black Americans are overrepresented among mass shooters by about the same proportion (a bit more than one-fourth) that whites are underrepresented. This means the population rate of mass shootings by whites (at least according to the tiny sample measured in the MoJo database) is 0.021 per 100,000 people, while the corresponding rate of mass shootings by blacks is 1.7 times higher, at 0.037