***CORRECTION: A FACEBOOK READER noticed something in the Mother Jones data I presented recently that I had missed. Beginning in 2013, MJ changed their definition of a mass public shooting from 4 or more victims to 3 or more victims in 2013 (see more below), but did not retroactively update their database. Although not deceptive (they said plainly they were doing this, I simply missed it), this is methodologically problematic. So I eliminated those cases, which reduces the total number in the database from 114 incidents to 95, and re-did the chart here.***
Gun trainer Rob Pincus texted to ask me tonight if I had any source for data on the seasonality of mass shooting activity. I.e., mass shootings by month.
I did not, but I was intrigued enough by the idea to do a little work when I got home tonight. The fruit of that labor is below. Important notes and interpretive points follow the chart.