Truth-Squadding the Gun Debate


[Mar. 7, 2013]  By now observers of the state legislature’s gun control fight have sat through more than 36 hours of debate in hearings and on the House floor, and Friday’s Senate votes will only add to that gargantuan total.

During all of that talk, facts and figures, claims and assertions have blizzarded from both sides, information that might succeed in persuading the public, if not lawmakers… if it’s true.

CPR set out to dissect four claims that have come up repeatedly in recent weeks, two from each side, to provide a little background to the rhetoric.  

[Listen to the audio for this story over at]


Claim # 1: 40% of people in the country who buy a gun today, don’t go through a background check.

Who’s Made It: Democratic lawmakers and witnesses in support of universal background checks.

How It Checks Out:  The Washington Post Fact Checker column looked into this figure and gave it two Pinocchios.

"It seems a little ridiculous that everyone’s quoting a number that’s two decades old," says Fact Checker columnist Glen Kessler. In addition to the study’s age, Kessler notes two other big problems: researchers only surveyed 251 people, and the 40% includes gun owners who weren’t sure whether they’d gone through a background check or not.

But it’s the age that really bothers Kessler.  ”A certain number of these people bought guns before we had instant background checks,” he points out. “The world has completely changed since that survey was done.”


Claim # 2: States that require background checks for private handgun sales have a 49% lower firearm suicide rate, and a 38% lower rate of women being shot to death by intimate partners than states that do not require such checks.

Who’s Made It: Retired ATF agent David Chipman, witness in favor universal background checks.

How It Checks Out:  Those figures comes from from the advocacy group Mayors Against Illegal Guns, which calculated both rates from 2010 numbers. Their dataset on domestic violence homicides is here, data for suicides came from the CDC.

The first thing to note is that background check laws varies widely from state to state. MAIG identifies 16 states as requiring background checks for private handgun sales. You can read summaries of their laws here.

To compare the rates of firearms suicides in states with or without background checks for private handgun sales, I did my own calculations using 2007 data from the University at Albany’s Criminal Justice Sourcebook, and came up with a difference in firearm suicide rates between stricter and looser background checks states that is very close to the MAIG’s finding. However, somewhere right now a statistic professor is yelling “correlation does not imply causation!”

When it comes to comparing rates of domestic violence shootings, things are trickier. One important factor is the (relative) rarity of that crime. Nationally, fewer than 700 women died that way in 2010.  One university statistician I spoke with cautioned strongly against drawing any state-by-state conclusions from a single year’s data.


Claim # 3: Most mass shootings have occurred in gun free zones, suggesting that killers target these places.

Who’s Made It: Republican lawmakers arguing against banning concealed weapons on college campuses and in favor of bills that allow or encourage carrying weapons in schools and more businesses. 

How It Checks Out:  For this claim I turned to Mother Jones magazines. Mother Jones is a decidedly liberal publication, but editors and reporters there have been compiling data on mass shootings since last year’s Aurora theater attack (listen to Senior Editor Mark Follman discuss their findings on NPR’s All Things Considered).

Using the descriptions of the 62 attacks listed in the dataset on their website, and supplemented by web searches for news articles about individual incidents, I tallied 40 instances when the shooter had a pre-existing relationship to the location of his or her attack, usually because they worked or went to school there, suggesting a more personal reason for their targeting.

Mother Jones Editor Follman says he’s yet to find any direct evidence of a mass shooter choosing the location for their spree based on its gun policy. And while he admits it’s possible accused Aurora shooter James Holmes picked the Century 16 movie theater because it barred guns (as some have argued), Follman says any attempt to divine attackers’ thinking on this issue “is based on a leap of logic” (Once again one thinks of cum hoc non proptor hoc)


Claim # 4:  Federally-contracted studies show the 10-year ban on assault weapons and larger capacity ammunition magazines had no beneficial effects on violent crime.

Who’s Made It: Dave Kopel, research director at the Independence Institute, arguing against Colorado’s bill limiting magazine size.

How It Checks Out:  In a 2004 study of the ban, researchers at the Urban Institute, a left-leaning Washington thinktank, found virtually no drop in how frequently large-capacity magazines were used in crimes, although they only analyzed data from four cities. However, the study blames the large number of high capacity magazines grandfathered into the ban and still in circulation for slowing any potential impact from the policy.

In writing about the future of the federal law, researchers concluded “Should it be renewed, the ban’s effects on gun violence are likely to be small at best and perhaps too small for reliable measurement.”