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Wednesday, September 9, 2015

Incomplete Data Used to Claim Few People Use Guns for Self-Defense

Jacob Sullum over at picks apart a new study by Harvard health policy professor David Hemenway and University of Vermont economist Sara Solnick that claims very few people use a firearm for defensive use:
A study in the latest issue of Preventive Medicine estimates that less than 1 percent of crime victims use guns in self-defense. The authors, Harvard health policy professor David Hemenway and University of Vermont economist Sara Solnick, find that using a gun seems to be effective at reducing property loss but "is not associated with a reduced risk of victim injury." It will surprise no one familiar with the long-running debate about defensive gun use (DGU) that the source of the data for this study is the National Crime Victimization Survey (NCVS), which consistently generates much lower DGU estimates than other surveys do. At least some of that gap can be plausibly explained by weaknesses in the NCVS that Hemenway and Solnick do not seriously address or, for the most part, even mention. 
That study is part of a special issue of Preventive Medicine titled Epidemiology and Prevention of Gun Violence where, according to the publication, "preventive medicine and health policy experts address a wide range of critical topics related to firearm violence, from the interaction of alcohol abuse with gun violence, effects of changes to gun laws in various states, how criminals obtain guns in a large US city, to how the public perceives gun violence and gun policies." 

Sullum points out that even though Hemenway and Solnick admit the data they are using can be misleading, it does not stop them from making the claim that there are very few people who use a firearm for self-defense.  Sullum says their interpretation is "too strong" because the NCVS may only represent a fraction of respondents involved in defensive gun uses, and, he points out that Florida State University criminologist Dr. Gary Kleck has more extensively addressed that point.
So what does research on the flaws in surveys of crime-related behaviors tell us? It consistently indicates that survey respondents underreport (1) crime victimization experiences, (2) gun ownership and (3) their own illegal behavior. While it is true that a few respondents overstate their crime-related experiences, they are greatly outnumbered by those who understate them, i.e. those who falsely deny having the experience when in fact they did. In sum, research tells us that surveys underestimate the frequency of crime victimizations, gun possession and self-reported illegal behavior...
So, as we have seen with other so-called studies that push gun control, this is just another example of cherry picking data in an attempt to prove a preconceived conclusion.

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