Mass Shooting Research Part 1; Mother Jones Data

This is part one of a four post series. The most recent post includes an after-Vegas data update, summary of all graphs, and possible solutions to the issue.

I get made fun of quite a bit for this, but one of my favorite things is crunching data using Pivot Tables and Charts in Excel. Doesn’t that sound fun? Sadly, I do enjoy it; exploring a massive set of data and making sense of it through Excel’s fantastic built in tools…good times. This is even more fulfilling when you can come up with unanswered questions about a noteworthy topic, then actually manage to find a set of data that might hold some answers. Along those lines, over the last few years I’ve wondered about mass shootings in the U.S., and specifically what the numbers would say about those events. There is a lot of political rhetoric on the topic, so it can be difficult to find evidence-based answers.

I’m actually not sure who originally came up with the definition, but law enforcement seems to define mass shooting events as “four or more shot and/or killed in a single event [incident], at the same general time and location, not including the shooter.” I was able to find two sources that have collected significant data on mass shooting events; Mother Jones magazine maintains a spreadsheet to support an article on the topic, and (GVA) also maintains yearly spreadsheets.

Interestingly, these two sources do not list the same events! Mother Jones’ data appears to contain only events that received national press coverage; 23 events from 2014 to June 2017, whereas documented 1146 events during that time frame. The flip side of that is Mother Jones’ data contains very detailed information, such as venue, mental health, weapons information, shooter demographics, and more. GVA only lists locations and number of victims, so each set of data has certain strengths and weaknesses. The plus for each is they are publicly available and can be downloaded by anyone who’s interested…like me!

I started by examining the Mother Jones’ data, so that’s where I’ll start here too. My curiosity on this topic primarily breaks down into two categories. First, what sort of weapons were used in mass shootings (and were they obtained legally)? Second, what were the motivations and mental health status of shooters? Unfortunately, motivation wasn’t explicitly stated in Mother Jones’ data, so I provided a designation based on their listed descriptions and summaries.

MS Events Per Year

Table 1. Mass Shooting Events per Year, Mother Jones Magazine Data.

MS Victims Per Year

Table 2. Mass Shooting Victim Counts by Year, Mother Jones Magazine Data.

MS Venue Types

Table 3. Venues/Locations for Mass Shootings, Mother Jones Magazine Data.

MS Weapon Types All

Table 4. Weapon Types Used in All Mass Shootings, Mother Jones Magazine Data.

MS Obtained Legally

Table 5. Weapons Legally Obtained for All Mass Shootings, Mother Jones Magazine Data.

MS WEapon Types by Year

Table 6. Weapon Types Used In Mass Shootings by Year, Mother Jones Magazine Data.

MS Ideology of Shooter

Table 7. Ideology of Shooters, Designated by the Writer, Derived from Descriptions in Mother Jones Magazine Data.

MS History of Mental Illness

Table 8. Prior History of Mental Illness, Mother Jones Magazine Data.

MS Ideology of Shooter by Year

Table 9. Ideology of Shooters by Year, Designated by the Writer, Derived from Descriptions in Mother Jones Magazine Data.

Some interesting conclusions jumped out at me from these graphs. The first is regarding frequency; as this data goes back to 1982, it does look like the number of events have increased over the last few years. Additionally, victims counts have increased. This is a good time to point out again the major weakness of the Mother Jones data; it is incomplete compared to our other source, so I’m not certain if this is trend can be extrapolated to all incidents that fit the mass shooting definition. Unfortunately, I was only able to obtain data going back to 2014, so it’s the best I’ve got at the moment for older events.

Another item that jumps out; mental illness is a significant issue in many of these shootings. Certainly, that’s not to stigmatize people who have mental illness; but it does seem to contribute to the instability these perpetrators suffer from. Personal grudges were the largest motivation, and many of the events involved a disgruntled employee (or former employee). I also have to point out that a few of these categories were difficult to determine, since there is overlap. For example, some stories that sounded like “personal grudges” may also have involved mental illness, and certain anti-police shooters also harbored racial motivations as well. I tried select the most emphasized aspect in Mother Jones’ spreadsheet, and in some instances, reviewed news articles for elaboration.

The mental illness component wasn’t really a surprise, but weapon use definitely was. I somewhat expected rifles to be the top weapon used in mass shootings, particularly the modular AR-style rifles seen in some of the more infamous events. The reality, however, seems to be that handguns are overwhelmingly the weapon of choice for shooters. And most of these were purchased legally.

In my next post, I’ll explore’s more extensive (but less detailed) list of shootings, as well as another category referred to by Wikipedia as “Rampage Killings.” I’ve also done some interesting data analysis on airplane seat sizes across different airlines (well, interesting to me anyway), and some other topics like computer graphics cards, cryptocurrencies (Bitcoin, Ethereum, etc), Washington D.C. neighborhoods, and other stuff. I’ll try to get posts on all of these Pivot Table crunching at some point!

Next Articles on this topic:

Part 2, Data and Rampages:

Part 3, State Comparisons:


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