Wednesday, December 2, 2015

Mass Shootings: How Scared Should You Be?

Note: I was just finishing this post when I heard about the tragic shooting in San Bernardino, California today. While it's vital that we take steps to prevent such horrors in the future, it's also vital that we don't live in fear because of them. To do so would be to let the murderers win, and besides, as I hope to demonstrate in this post, mass shootings aren't a very significant risk for most people. We should respond to them with concrete, effective steps to prevent more of them, not with unwarranted fear and paranoia. 

I've never thought it made sense for me to worry about becoming the victim of a random mass shooting. First, worry alone has precisely zero effect on whether it will happen or not. All it does is make you more anxious and less happy. Second, I've always figured that if I do die before my time, it's far more likely that it will be from something like cancer or a car accident. As awful as mass shootings are, and as much as they need to be minimized, the average person's chance of dying that way are pretty small.

Unfortunately, a lot of people don't realize that. This is mostly due to a sensationalist mass media, and to a cognitive bias known as the availability heuristic. It's called that because humans estimate the prevalence of things by how easily examples of them come to mind--how "available" they are to consciousness. The problem with that, especially in a media-saturated age, is that unusually scary and disturbing events stick in our minds, giving us the illusion that they're far more common than they really are.

Knowing this, I've never gotten very worried about being the victim a mass shooting (or a terrorist, shark, or bear attack). But the other day, I finally succumbed just a little bit to the fear of mass shootings that has gripped the country in the last few years. I live in Colorado, where two of the most notorious mass shootings occurred: Columbine and the Aurora theater shooting. And now, this past Friday, a man in Colorado Springs went on a shooting rampage at a Planned Parenthood, killing 3 and wounding 9. Also, I work in an urban public library, so I deal with all walks of life--including some rather scary-looking and poorly adjusted people. So, I finally caught a little of the fear. I don't like to admit it, but I did. I started looking at some of the mentally unstable people I see every day, and wondering how likely it is that one of them could pull out a gun and start shooting.

So, I decided to look at some actual numbers, to check whether I was being silly or not. I wanted to look up the actual numbers of people killed and injured by mass shootings, and see they compare to the number of people killed and injured in car wrecks, plane crashes, falls, and so on. Since the numbers take some explaining, and are rather grim, here's the quick answer: I was, in fact, being silly. The average American should worry MUCH less about mass shootings than about car wrecks, accidental poisonings, drowning, and many other things--and you're really not that likely to die in those ways if you're healthy and careful. Yes, it's good to know what to do in an active shooter situation, but what really makes you safer are mundane things like watching your weight, not smoking, wearing a seat belt, and not abusing drugs or alcohol.

Now for the more in depth look at the numbers. When I started researching mass shootings, I quickly ran into a small problem, because different definitions of "mass shooting" yield dramatically different answers about how common they are. For example, the Congressional Research Service has a report that borrows the FBI's definition of "mass murder" for mass shootings, defining them as a shooting where four or more people are killed. The chart below is a summary of their data, which runs from 1999 through 2013.
Based on these numbers, there's been an average of just over 20 mass shootings per year during this time period, with around a hundred people killed per year. However, these aren't exactly the figures we're looking for, because they include incidents that aren't what most people worry about when they worry about themselves or their loved ones becoming victims of public mass shootings, including gang violence and other criminal activities, and mass shootings within families. Those are terrible things, of course, but they're different than mass shootings in public places, as in things like the Aurora theater shooting.

To get at those kinds of shootings, the CRS also looked at "Public Mass Shootings", which they defined as incidents in which "four or more victims were shot to death in one or more public locations, such as a workplace, school, restaurant, house of worship, or neighborhood, and the murders were not attributable to any underlying criminal activity or commonplace circumstance (e.g., armed robbery, criminal competition, insurance fraud, argument, or romantic triangle)". Here's a graph on that kind of event:


These data look a little less awful. The table below breaks down some of the statistical trends:


According to this definition of a mass shooting, there was an average of 4.2 incidents per year between 1999 and 2008, increasing to 4.8 from 2009-2013 (due mostly to a spike in 2012). The number of deaths and injuries per year also increased in that last five year period, with noticeably more victims killed, and twice as many (on average) wounded.

Looking at the numbers this way, it seems that the chance of being a mass shooting victim is quite small. Even in the last five years, when both shootings and casualties increased, there was an average of 70.4 casualties per year--in a country with over 300 million people. If you're like me, you don't have a visceral sense what 300 million actually means. To put it in perspective, if you tried to count every person in the US (counting around the clock) you would be at it for over a decade. If you tried to count the number of people killed in mass shootings in a year, it would take about a minute. So, your chance of being the victim of a public mass shooting, as defined by the Congressional Research Service, is infinitesimally small.

However--the CRS definition seems a good bit too restrictive to me. Using their criteria, for example, the recent Planned Parenthood shooting in Colorado Springs wouldn't count as a public mass shooting, because "only" three people were killed. But we all know this was the kind of event that most people think of as a mass shooting. The same is true of an event where multiple people are shot, but somehow nobody is killed. So how do we account for these "lesser" shootings?

Unfortunately, it's not easy to do. I haven't been able to find a data set that accounts for mass shooting incidents where less than 4 people are killed, but which also distinguishes "mass public shootings" from family shootings or things like gang shootouts. The closest thing I've found is the Mass Shooting Tracker, which is a crowd-sourced website that tracks any event in which more than 4 people are shot and injured, but not necessarily killed. While it is crowd-sourced--and should therefore be taken with some grains of salt--it does link each incident to a news report, so it's fairly credible. The problem is that it doesn't distinguish "public mass shootings" from other types of shooting in the same way the Congressional Research Service does, so, while the CRS data underestimate the numbers, the Mass Shooting Tracker overestimates them. But it's still well worth looking at, as a counterpoint to the CRS report.

According to the Mass Shooting Tracker, as of November 27 there had been 352 mass shootings in 2015, resulting in 447 deaths and 1292 injuries. Obviously, that's a lot more than the numbers we see with the CRS. It's not that the CRS is being dishonest--they're just using a far more restricted definition of mass shootings. In my opinion, the data set we really need is somewhere between the two, and would restrict the incidents to the kind of public shooting we are concerned with here, while tracking every such incident where 4 or more people are injured.

But we don't have those numbers, so perhaps the best we can do is split the difference, and take the average between the two data sets. Let's look at the Mass Shooting Tracker data for 2013, since it's a full year's worth of data. In that year there were 364 mass shootings, with 502 people killed and 1266 injured. Let's take the average of these numbers with the numbers from the CRS for the last five years of their data. That's comparing apples and oranges, really, but it's the best we can do.

This gives us the following sad numbers: 288 deaths, and 666 injuries (roughly) per year in recent years. Now the question is, how does this compare to the risk of being killed in other kinds of incidents, such as car accidents, falls, etc.? (It would get too complicated to compare non-fatal injuries, because it's tough to decide what counts as a significant injury). Here are some numbers for comparison. In the year 2013, these are the unintentional injuries that kill the most people, from the Centers for Disease Control:


You might be surprised (I was) to see that the leading cause of accidental death these days is poisoning--mostly overdoses on prescription drugs. In 2013, the average person was about 134 times as likely to die by accidental poisoning as by public mass shooting. Going by the restrictive CRS definition of a public mass shooting, the average person was 1042 times more likely to die by poisoning. Even with my more expansive estimate of public mass shootings, as many people die every three days by poisoning as all year by mass shooting. Next down the scale are motor vehicle accidents and falls, which kill 117 and 105 times as many people, respectively, as mass shootings. According to these numbers, the average person is slightly less likely to die in a mass shooting than they are to die in a bicycle accident. How often do you hear people worrying themselves sick over bicycle accidents?

Again, my point is NOT that mass shootings, or gun violence in general, aren't a problem in this country. They're absolutely a problem, and one that needs to be dealt with. My point is just that it doesn't make sense for the average person, who isn't involved in violent criminal activity or part of  a family with violence-prone members, to spend their days worrying about themselves or their loved ones dying in a mass shooting. It makes much more sense to worry about the things that are far more dangerous, like riding in cars and on motorcycles, abusing prescription drugs, getting old and falling, drowning, and so on. Better yet, stop worrying and take concrete steps to minimize the risks (see chart in the notes*). The same goes for diseases like heart disease, which kills over five times as many people as all unintentional injuries combined, and 2,122 times as many people as mass shootings.

Does it make sense to be sad about mass shootings? Certainly. Does it make sense to be angry, and angry with politicians who won't lift a finger to stop them? Absolutely. Does it make sense to live in fear of mass shootings? Absolutely not.

But...does that mean the United States doesn't have a problem with gun deaths? Unfortunately, no. In 2013, 11,208 people were murdered with guns (over three times as many people murdered as drowned). Another 21,175 people committed suicide with a gun, and 505 people were accidentally killed by guns. It's clearly a problem, and mass shootings are a part of that problem, albeit a much smaller one than most people think.

Still, even with our unconscionably high rate of gun homicide in the US compared to other developed countries, homicide is not a very common way to die, especially for people who aren't involved in violent criminal activity. According to the National Safety Council's sanity-promoting Odds of Dying chart, the average person has a 1 in 358 chance of being murdered with a firearm. That's much too high, but you're still 3 times as likely to die in a car wreck, and 51 times as likely to die from a heart attack or cancer. Mass shootings are a tragic, awful problem in our country, but they aren't worth living in fear over--especially since living in fear is letting the bastards win. I don't know about you, but I'm not going to do that.

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* To take concrete steps to minimize the risk of various kinds of diseases and injuries, you need to know what which ones happen at different ages. Falls, for example, are a much bigger risk for older people than anyone else. The chart below shows what injury-related deaths are most prevalent for people of different age groups. To see totals for the population as a whole, see the far right column.


This data, and most of the injury data in this post, comes from the CDC's WISQARS statistics site, which is very much worth taking a look at.