More Holes in the Defensive Gun Use Myth: New Study Finds DGU is Ineffective and Rare

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A recent study published in The Journal of Preventive Medicine offers new support for the argument that owning a gun does not make you safer. The study, led by David Hemenway, Ph.D., of the Harvard T.H. Chan School of Public Health, examines data from the National Crime Victimization Survey — an annual survey of 90,000 households — and shows not only that so-called “defensive gun use” (DGU) rarely protects a person from harm, but also that such incidents are much more rare than gun advocates claim.

A 2014 Gallup poll suggests that Americans increasingly perceive owning firearms as an effective means of self-defense — having a gun makes one less likely to become a victim of a crime. But as Hemenway’s study demonstrates, this belief is not supported by crime statistics. Contrary to what many gun advocates argue, the National Crime Victimization Survey (NCVS) data reveals that having a gun provides no statistically significant benefit to a would-be victim during a criminal confrontation.

The study found that in incidents where a victim used a gun in self-defense, the likelihood of suffering an injury was 10.9 percent. Had the victim taken no action at all, the risk of injury was virtually identical: 11 percent. Having a gun also didn’t reduce the likelihood of losing property: 38.5 percent of those who used a gun in self-defense had property taken from them, compared to 34.9 percent of victims who used another type of weapon, such as a knife or baseball bat.

What’s more, the study found that while the likelihood of injury afterbrandishing a firearm was reduced to 4.1 percent, the injury rate after those defensive gun uses was similar to using any other weapon (5.3 percent), and was still greater than if the person had run away or hid (2.4 percent) or called the police (2.2 percent). These results were similar to previous research on older NCVS data which showed that, while using a firearm in self-defense did lower a person’s risk of subsequent injury, it was less effective than using any weapon other than a gun.

As Hemenway notes, however, the one time having a gun does significantly lower injury rates is before the individual takes a defensive action. This seemingly bizarre result can be explained in one of two ways: People carrying a gun could be more vigilant and aware of their surroundings, and therefore better able to avoid an initial attack. Alternatively, it could mean that the types of crime stopped by a defensive gun use are substantively different from the types of crime stopped when some other protective action is taken. Rather than circumstances where a victim is attacked by surprise, and thus more likely to be injured before taking protective action, incidents where a gun is used in self-defense could mainly involve mutually hostile confrontations that end in verbal or physical aggression.

Indeed, the latter explanation is supported by a pair of private surveys conducted by Hemenway in 1996 and 1999, in which respondents were asked to describe DGUs in their own words, found that the majority of defensive gun uses were both illegal and provided no social benefit. Across these two large national samples of randomly selected telephone numbers, the conclusion was overwhelming: “Guns are used to threaten and intimidate far more often than they are used in self-defense. Most self-reported self-defense gun uses may well be illegal and against the interests of society.”

The surveys also found that when someone uses a gun in self defense, it is often part of an escalating hostile interaction — one in which both participants are likely to be responsible for the event that initially prompted the DGU. One male respondent who reported a defensive gun use described an incident as follows: “I was watching a movie and he interrupted me. I yelled at him that I was going to shoot him and he ran to his car.” Another respondent pulled out a gun to resolve a conflict with his neighbor: “I was on my porch and this man threw a beer in my face so I got my gun.”

It is not at all clear that cases such as these are in the public interest — let alone constitute legitimate defensive gun use. After all, these incidents are substantially different from a situation in which a victim is taken by surprise, such as during a street mugging.

In his new NCVS study, Hemenway also found that defensive gun use is exceedingly infrequent. While smaller private surveys estimated that there are up to 2.5 million DGUs on an annual basis, the NCVS data indicates that victims used guns defensively in less than 1 percent of attempted or completed crimes, with an annual total of less than 70,000.

By using the NCVS data, Hemenway’s analysis has several key advantages over other study examining DGUs. Even the best-designed surveys fail to produce reliable estimates for defensive gun use because they inadvertently capture a large number of false positives, producing final estimates that don’t comport with reality. The most famous one-off study on this subject, conducted by criminologists Gary Kleck and Mark Gertz in 1992, estimated that guns are used 2.5 million times a year in self-defense. But as we’ve written before, we now know that number to be mathematically impossible in light of reliable empirical data like hospital records, victimization surveys, gun violence archives, and police records.

The NCVS study corrects for the methodological weaknesses that plague private surveys by asking follow-up questions on self-defense use only after a respondent answered affirmatively to the question of whether or not they had been a victim to an attempted or completed crime. This strategy decreases the likelihood of false positives because it removes many opportunities for a respondent to exaggerate or manufacture a self-defense claim. The NCVS also corrects for telescoping, which occurs when a respondent incorrectly remembers a legitimate defensive gun use that took place outside of the time frame covered in the survey. For instance, a respondent may describe a confrontation that happened a year ago in response to a question asking about defensive gun use only in the last six months. By lumping in incidents from outside the study period, telescoping can inflate rates of the behavior being tallied.

Despite these advantages, even the NCVS is almost certainly overestimating defensive gun use. The fact is that defensive gun use is an inherently rare phenomenon: Any survey, no matter how well designed, will produce a final estimate that is much higher than its true incidence because of false positives. Not only is this a well-established statistical phenomenon, it’s also supported by new data from the Gun Violence Archive (GVA) — the most comprehensive and systematic effort to catalog every publicly available defensive gun use report — which finds that there were fewer than 1,600 verified DGUs in 2014.

In response to GVA data, pro-gun advocates have been forced to argue that the reason researchers can barely find .064 percent of the 2.5 million DGUs a year claimed by Kleck and Gertz is because virtually nobody reports their defensive gun use to the police. This argument is problematic. For starters, it would seem to imply that the vast majority of people using guns in self-defense are irresponsible citizens who use their firearm to ward off an attempted crime, and then, perhaps uncertain about the legality of their action, are leery of interacting with the police. It would also imply that while these citizens ostensibly stopped a crime serious enough to justify brandishing a firearm, they aren’t at all concerned about informing the police about a criminal who remains on the street.

Even more problematically, Kleck’s own survey indicates that police knew about 64% of DGUs.  And other studies come to similar numbers.  So if Kleck’s study is correct, we should find nearly 1 million police and media reports each year, and more than 25,000 if the NCVS is correct.    The fact that we’re not finding empirical support of defensive gun uses demonstrates unequivocally that such estimates are wrong.  It is instructive that gun advocates cling to Kleck’s figure that guns are used “2.5 million times a year”, insisting that his survey somehow got that number exactly right, but conveniently overlook the figure from the very same survey on police reports, which is demonstrably off by a factor of nearly 1000.   

The only thing we can know for sure is what we have empirical data on: Namely, that there is a reliable floor for defensive gun use estimates at around 1,600 a year. In addition, according to the most recent data on defensive gun use, we have reliable evidence showing that owning a firearm does not give individuals any significant advantage in a criminal confrontation, and they are no less likely to lose property or be injured by using a gun in self defense.

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