You know less than you think about guns: the misleading uses, flagrant abuses, and shoddy statistics of social science about gun violence.

• Author: Doherty, Brian

"THERE IS A GUN for roughly every man, woman, and child in America," President Barack Obama proclaimed after the October mass shooting that killed 10 at Umpqua Community College in Oregon. "So how can you, with a straight face, make the argument that more guns will make us safer? We know that states with the most gun laws tend to have the fewest gun deaths. So the notion that gun laws don't work--or just will make it harder for law-abiding citizens and criminals will still get their guns--is not borne out by the evidence."

In this single brief statement, Obama tidily listed the major questions bedeviling social science research about guns--while also embodying the biggest problem with the way we process and apply that research. The president's ironclad confidence in the conclusiveness of the science, and therefore the desirability of "common-sense gun safety laws," is echoed widely with every new mass shooting, from academia to the popular press to that guy you knew from high school on Facebook.

In April 2015, the Harvard gun-violence researcher David Hemenway took to the pages of the Los Angeles Times to declare in a headline: "There's scientific consensus on guns--and the NRA won't like it." Hemenway insisted that researchers have definitively established "that a gun in the home makes it a more dangerous place to be...that guns are not used in self-defense far more often than they are used in crime...and that the change to more permissive gun carrying laws has not reduced crime rates." He concludes: "There is consensus that strong gun laws reduce homicide."

But the science is a lot less certain than that. What we really know about the costs and benefits of private gun ownership and the efficacy of gun laws is far more fragile than what Hemenway and the president would have us believe.

More guns do not necessarily mean more homicides. More gun laws do not necessarily mean less gun crime. Finding good science is hard enough; finding good social science on a topic so fraught with politics is nigh impossible. The facts then become even more muddled as the conclusions of those less-than-ironclad academic studies cycle through the press and social media in a massive game of telephone. Despite the confident assertions of the gun controllers and decades of research, we still know astonishingly little about how guns actually function in society and almost nothing at all about whether gun control policies actually work as promised.

Do More Guns Mean More Homicides?

"More Americans have died from guns in the United States since 1968 than on battlefields of all the wars in American history," New York Times columnist Nicholas Kristof wrote on August 26, 2015, just after the grisly on-air murder of two television journalists in Virginia. It's a startling fact, and true.

But do the number of guns in circulation correlate with the number of gun deaths? Start by looking at the category of gun death that propels all gun policy discussion: homicides. (Gun suicides, discussed further below, are a separate matter whose frequent conflation with gun crime introduces much confusion into the debate.)

In 1994 Americans owned around 192 million guns, according to the U.S. Justice Department's National Institute of Justice. Today, that figure is somewhere between 245 and 328 million, though as Philip J. Cook and Kristin A. Goss in their thorough 2014 book The Gun Debate: What Everyone Needs to Know (Oxford University Press) wisely concluded, "the bottom line is that no one knows how many firearms are in private hands in the United States." Still, we have reason to believe gun prevalence likely surpassed the one-gun-per-adult mark early in President Barack Obama's first term, according to a 2012 Congressional Research Service report that relied on sales and import data.

Yet during that same period, per-capita gun murders have been cut almost in half.

One could argue that the relevant number is not the number of guns, but the number of people with access to guns. That figure is also ambiguous. A Gallup poll in 2014 found 42 percent of households claiming to own a gun, which Gallup reports is "similar to the average reported to Gallup over the past decade." But those looking for a smaller number, to downplay the significance of guns in American life, can rely on the door-to-door General Social Survey, which reported in 2014 that only 31 percent of households have guns, down 11 percentage points from 1993's 42 percent. There is no singular theory to explain that discrepancy or to be sure which one is closer to correct--though some doubt, especially as gun ownership continues to be so politically contentious, that people always reliably report the weapons they own to a stranger literally at their door.

The gun murder rate in 1993 was 7.0 per 100,000, according to the Centers for Disease Control and Prevention's (CDC) National Center for Injury Prevention and Control. (Those reports rely on death certificate reporting, and they tend to show higher numbers than the FBI's Uniform Crime Reporting program, though both trend the same.) In 2000 the gun murder rate per 100,000 was 3.8. By 2013, the rate was even lower, at 3.5, though there was a slight upswing in the mid-00s.

This simple point--that America is awash with more guns than ever before, yet we are killing each other with guns less than ever before--undermines the narrative that there is a straightforward, causal relationship between increased gun prevalence and gun homicide. Even if you fall back on the conclusion that it's just a small number of owners stockpiling more and more guns, it's hard to escape noticing that even these hoarders seem to be harming fewer and fewer people with their weapons, casting doubt on the proposition that gun ownership is a political crisis demanding action.

In the face of these trend lines--way more guns, way fewer gun murders--how can politicians such as Obama and Hillary Clinton so successfully capitalize on the panic that follows each high profile shooting? Partly because Americans haven't caught on to the crime drop. A 2013 Pew Research Poll found 56 percent of respondents thought that gun crime had gone up over the past 20 years, and only 12 percent were aware it had declined.

Do Gun Laws Stop Gun Crimes?

The same week Kristof's column came out, National Journal attracted major media attention with a showy piece of research and analysis headlined "The States With The Most Gun Laws See The Fewest Gun-Related Deaths." The subhead lamented: "But there's still little appetite to talk about more restrictions."

Critics quickly noted that the Journal's Libby Isenstein had included suicides among "gun-related deaths" and suicide-irrelevant policies such as stand-your-ground laws among its tally of "gun laws." That meant that high-suicide, low-homicide states such as Wyoming, Alaska, and Idaho were taken to task for their liberal carry-permit policies. Worse, several of the states with what the Brady Campaign to Prevent Gun Violence considers terribly lax gun laws were dropped from Isenstein's data set because their murder rates were too low!

Another of National Journal's mistakes is a common one in gun science: The paper didn't look at gun statistics in the context of overall violent crime, a much more relevant measure to the policy debate. After all, if less gun crime doesn't mean less crime overall--if criminals simply substitute other weapons or means when guns are less available--the benefit of the relevant gun laws is thrown into doubt. When Thomas Firey of the Cato Institute ran regressions of Isenstein's study with slightly different specifications and considering all violent crime, each of her effects either disappeared or reversed.

Another recent well-publicized study trying to assert a positive connection between gun laws and public safety was a 2013 JAMA Internal Medicine article by the Harvard pediatrics professor Eric W. Fleegler and his colleagues, called "Firearm Legislation and Firearm-Related Fatalities in the United States." It offered a mosdy static comparison of the toughness of state gun laws (as rated by the gun control lobbyists at the Brady Center) with gun deaths from 2007 to 2010.

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