Mathematical Questions: Guns Yet Again

I’m not going to call this mathematical malpractice because I don’t think it’s been reviewed or published yet. But the way the study is quoted in the press makes me highly dubious of its conclusions:

There are approximately 7,500 child hospitalizations and 500 in-hospital deaths each year due to injuries sustained from guns. In an abstract presented Oct. 27 at the American Academy of Pediatrics (AAP) National Conference and Exhibition in Orlando, researchers also identified a link between the percentage of homes with guns and the prevalence of child gunshot injuries.

In “United States Gunshot Violence—Disturbing Trends,” researchers reviewed statistics from the Kids’ Inpatient Database (KID) from 1997, 2000, 2003, 2006 and 2009 (for a total of 36 million pediatric hospital admissions), and estimated state household gun ownership using the most recent Behavioral Risk Factor Surveillance System data (2004).

The study found that approximately 7,500 children are admitted to the hospital for the treatment of injuries sustained from guns each year, and more than 500 children die during hospital admission from these injuries. Between 1997 and 2009, hospitalizations from gunshot wounds increased from 4,270 to 7,730, and in-hospital deaths from 317 to 503.

Several things that raise alarm bells:

  • The study is of five very specific years rather than of all twelve years.
  • The study using the KID database for hospitalizations. Looking over the details of this database shows that these five years are the only years in the database (which is apparently compiled every three years). However, the number of participating hospitals has increased over time. This could induce a variety of biases, not all of which are obvious. It could also be biased by an increasing tendency to hospitalize gunshot victims. It could also be biased because KID, after 1997, uses a larger age range, adding 18- and 19-year olds who are more likely to be engaged in criminal activity. I’d have to see the paper to see how they have accounted for these. I suspect the biases are very strong compared to the overall signal and the reliability of the result is critically dependent on how they account for the biases.
  • The press release does not specify an age range but KID tracks patients up to age 18 (in 1997) and age 20 (from 2000 on). This isn’t exactly what people think of with “kids” and this age range has been used before to inflate the number of kids who are victims of gun violence.
  • The trend of massively increasing violence is the complete opposite of what every study of criminal violence is showing. Murder is down, assault is down, gun violence is down down down according to crime states, FBI stats and victim surveys.
  • I’m not here to slander anyone’s work. They may already have addressed the points I raise above. My read is that this is an abstract, not a refereed paper. So all I can do is point out the obvious pitfalls that might be causing this abstract to contradict everything else we know about violent crime. The gun control side, as I have documented on this blog, has a history of twisting the stats, sometimes unintentionally. And the media have a tendency to exaggerate the results of tentative early studies when it suits their narrative.

    (The gun control side also has a history of outright fraud but I am very dubious that any fraud is occurring here because it would be too easy to check. They are using a public database, not proprietary data.)

    There’s also the Scientific Peter Principle to consider here. If you hear of a study with startling results, it is most likely to be erroneous. That goes doubly so for unrefereed abstracts presented at conferences. The reason is that errors and biases almost always give you unexpected results. For veteran scientists, that’s often how you spot biases but even the best scientists can be fooled. That this study indicates a massive increase in violence at a time when every other study indicates that violence is falling (as is gun ownership) causes me to be concerned that something is wrong.

    Two things I would place small bets on. Within a few months, this study will be shown to be flawed in some way and its conclusions toned down. And for the next ten years, the initial abstract will be quoted by gun control advocates as proof of their position (e.g., the selective quoting of Mother Jones).

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