The shooting in San Bernardino, California, on Wednesday was the 353rd mass shooting of 2015, according to the crowdsourced Mass Shooting Tracker that Vox uses for our maps documenting mass shootings. Or it was the 29th, if you use data from USA Today. Or it was the fourth, if you use a database maintained by Mother Jones.

How are three news outlets coming up with such different answers? It all comes down to definitions:

The Mass Shooting Tracker defines a mass shooting as an event in which four or more people were shot .

USA Today tracks mass killings , in which four or more people were killed .

, in which . Mother Jones tracks mass killings in which four or more people were killed but excludes "gang activity, armed robbery, or domestic violence."

There are other differences too — for example, Mother Jones says it generally only includes single gunman incidents, though it includes San Bernardino and the Columbine massacre in its database. But those are the main ones.

What's happening here a dispute not about the facts, but over what the appropriate definition is.

Why people care which definition is used

The Mass Shooting Tracker definition is fairly new, but the dispute between Mother Jones and USA Today is older and more ideologically fraught. That's because the Mother Jones definition suggests that mass shootings are rising in number, and the USA Today definition doesn't.

If you look at all killings in which four or more people died, there doesn't appear to be a strong upward trend, according to estimates by Northeastern University criminology professor James Alan Fox, who uses a similar definition to USA Today:

But other researchers, like Amy P. Cohen, Deborah Azrael, and Matthew Miller of the Harvard School of Public Health, argue that Mother Jones's more restrictive definition is appropriate. Cohen et al. analyzed Mother Jones's data and concluded that mass shootings were becoming more frequent. They 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:

Which is the right definition to use?

So who's right? Well, Fox is right about the phenomenon he's studying, Cohen et al. are right about the phenomenon they're studying, and the Mass Shooting Tracker is right for the phenomenon it's studying. Declaring one or the other definition the "right" one is too pat; each is right for the thing it tracks. 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. And the Mass Shooting tracker tells us that mass shootings, deadly or not, are a daily occurrence in the US; that is, obviously, 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, in particular, 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.

The best case for gun control has little to do with mass shootings, and isn't necessarily focused on homicides at all

What's frustrating about this is that whether mass shootings are increasing or decreasing in frequency has very little to do with the generalized case for gun control. Mother Jones's Mark Follman — who has done extraordinary work on gun violence in America, including compiling the data set used by Cohen et al. — is not wrong when he writes that the Mother Jones–defined mass shootings are "a unique phenomenon that must be understood on its own." And it's worth studying both the phenomena identified by Fox and those identified by Mother Jones 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 with 11,068 total gun homicides in 2011); by the Mother Jones definition, there are substantially fewer than that.

The real case for gun control

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. Of the 33,636 firearm deaths in 2013, 63 percent, or 21,175, 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 that 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 then 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."

America's gun homicide problem is real, frightening, and must be addressed. But its gun suicide problem is considerably worse.

Guns make it likelier that these impulsive decisions end in death rather than in 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 or 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.

VIDEO: America's gun problem explained in 90 seconds