Are Mass Public Shootings Seasonal? (Corrected)

***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.

Why Surveys Underestimate Gun Ownership Rates in the U.S.

I concluded a recent post saying if anyone ever asks you how many gun owners there are in America, you can tell them AT LEAST: 40% of households in America have guns in them and 30% of individuals in America personally own a gun.

Saying AT LEAST is crucial here, because these figures underestimate the actual rate of gun ownership in the United States. How badly they underestimate gun ownership we do not and cannot know precisely. My educated guess is that the underestimate is at least 10%, that 25% would not be an unreasonable amount, and more than 25% is likely.

So, if anyone ever asks you how many gun owners there are in America, you can tell them, No one really knows but PROBABLY:

44 to 50% of households (or more) in American have guns in them

33 to 37% of individuals (or more) in America own a gun

Widely circulated internet meme. Unattributed.