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Are mass shootings really on the rise? It depends how you count.

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Dylan Matthews is a senior correspondent and head writer for Vox's Future Perfect section and has worked at Vox since 2014. He is particularly interested in global health and pandemic prevention, anti-poverty efforts, economic policy and theory, and conflicts about the right way to do philanthropy.

Northeastern criminologist James Alan Fox claims that mass shootings aren't increasingin the US. Researchers Amy P. Cohen, Deborah Azrael, and Matthew Miller of the Harvard School of Public Health argue they are, in fact, increasing. Both are correct.

Sometimes, in policy debates, there are strong disagreements about actual facts about the topic at hand. A defining feature of the climate change debate is that roughly half of the American political spectrum refuses to concede that climate change is even happening. In those cases either one side is simply wrong (as in the climate change example), or else the issue is extremely hard to study and reach definite conclusions about. But much more common than straight-up factual disputes are disputes over interpretation. That's what's happening with Fox and the Harvard researchers.

Fox uses a pretty straightforward definition of "mass shooting": shootings in which at least four people die. And by that definition, he's right: shootings of four or more people haven't been on a clear upswing. They haven't been on a clear downswing either, which one might have expected in light of the overall decline in gun violence over the past twenty years; while the rate is highly variable, the trend line has stayed roughly flat in recent decades:

no mass shooting increase

(James Allan Fox)

Cohen et al argue that that definition is too simple. "[Fox's] analysis," they write, "which counts the number of events per year, lumps together mass shootings in public places with a far more numerous set of mass murders that are contextually distinct — a majority of which stem from domestic violence and occur in private homes." It's true — most mass shootings are committed in a context of domestic or gang violence, and so those make up most of Fox's dataset.

But Cohen et al want to restrict the definition further. They use data compiled by Mother Jones on mass shootings, which "exclude[s] mass killings in private homes related to domestic violence as well as attacks stemming from drug and gang-related activity." Once they've zeroed on non-domestic/gang/drug violence mass shootings, Cohen et al then measure the average period of time between mass shooting incidents, rather than the number of incidents themselves; mass shootings of the kind they're studying are rare enough to make the latter untenable. They find that the period of time separating mass shootings (by their definition) has been shrinking:

mother jones mass shootings

(Amy P. Cohen, Deborah Azrael, Matthew Miller / Mother Jones)

Does it matter what definition we use?

So who's right? Well, Fox is right about the phenomena he's studying, and Cohen et al are right about the phenomenon they're studying. Declaring one or the other definition the "right" one is too pat; each is right for the thing it's right for. Fox's data tells us that shootings of four or more people didn't decline in the 1990s the way shootings as a whole did; that's concerning. Cohen et al's data tells us that high profile public mass shootings like Aurora or Newtown have not only failed to decline the way normal shootings have, but have increased in recent years; that's also concerning.

But people still care about determining the "right" definition in cases like this for the purpose of ideological proxy warfare. Declaring Fox or Cohen et al right has a certain political valence in the wider gun control debate. You see something similar in discussions around school shootings, wherein gun control skeptics are as eager to declare that gang-related shootings in school are not real school shootings as they are to embrace Fox's definition in which gang-related mass shootings are real mass shootings — and vice versa for gun control supporters.

What's frustrating about this is that whether or not mass shootings are increasing or decreasing in frequency has very little to do with the generalized case for gun control. Mother Jones' Mark Follman — who has done extraordinary work on gun violence in America, including compiling the dataset used by Cohen et al — is not wrong when he writes, "The question of whether public mass shootings can be prevented hinges on understanding the complex factors behind them." And it's worth studying both the phenomena identified by Fox and that identified by Cohen et al to find specialized ways to prevent them. But mass shootings are very rare. By Fox's definition, there are between 50 and 125 victims a year (compared to 11,068 total gun homicides in 2011); by the Mother Jones definition, there are substantially fewer than that.

The real case for gun control

gun homicide suicide rate

Mass shootings can and should be prevented, and their comparative rarity makes them no less monstrous or tragic. But the best case for gun control has little to do with mass shootings, and isn't necessarily focused on homicides at all. 19,990 of the 32,351 firearm deaths (61.8 percent) in 2011 were suicides. The evidence that the presence of additional guns contributes to more firearm homicides is persuasive, but research from the Means Matter Project at the Harvard School of Public Health (much of it done by Azrael and Miller themselves, along with Cathy Barber) shows that the evidence guns contribute to higher levels of suicide is considerably stronger.

Suicide, contrary to popular belief, isn't typically planned and thought through extensively in advance. It's impulsive; one survey found that 90 percent of respondents deliberated for less than a day before attempting suicide. And 90 percent of people who survive suicide attempts end up dying by other means. They didn't make a considered choice and seek to follow through by whatever means; they made an impulsive decision and got lucky. Ken Baldwin, who survived a jump off the Golden Gate Bridge, once told the New Yorker's Tad Friend that as he was falling, he "instantly realized that everything in my life that I’d thought was unfixable was totally fixable — except for having just jumped."

Guns make it likelier that these impulsive decisions end in death rather than survival and recovery. Studies suggest that suicide attempts using guns are fatal in the vast majority of cases, while attempts using cuts or poisoning are only fatal 6-7 percent of the time. So it's perhaps unsurprising that areas with more guns tend to have higher suicide rates, or that a number of gun control measures have been successful in preventing suicides. In one particularly dramatic case, the Israeli Defense Forces stopped letting soldiers bring their guns home over the weekend, and suicides fell 40 percent, primarily due to a drop in firearm suicides committed on weekends.

The dominant focus of gun control efforts, then should be on keeping guns (and particularly handguns) out of the hands of suicidal people. America's gun homicide problem is real, frightening, and must be addressed. But its gun suicide problem is considerably worse. My concern is that disputes over whether this or that incident counts as a mass shooting reaffirms the myth that Jared Loughner and Adam Lanza are the face of America's gun violence problem. They're not. The tens of thousands who die every year because of depression and a nearby gun are. They are rarely if ever mentioned in the gun debate, and they deserve better.

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