Friday, May 25, 2012

Watch the definitions

A quick one for a Friday:

I've blogged before about paying careful attention to the definition of words used in study results.  It is often the case that the definition used in the study/statistic may not actually match what you presume the definition is.

Eugene Volokh posted a good example of this today, when he linked to this op-ed in the Detroit Free Press.  It cites a spokesperson from the Violence Policy Center who states that "Michigan is one of 10 states in which gun deaths now outpace motor vehicle deaths".

My knee jerk reaction was that seemed high, but my tired Friday brain probably would have kept skimming.  Then I read why Volokh was posting it:
The number of accidental gun deaths in Michigan in 2009 (the most recent year reported in WISQARS) was … 12, compared to 962 accidental motor-vehicle-related deaths. 99% of the gun deaths in Michigan that year consisted of suicides (575) and homicides (495).
To be honest, I had presumed homicides were included, but suicide death didn't even occur to me.   I'd be interested to see how many of the vehicular deaths were suicides, my guess is the percentage would not be as high as in the gun case.  Either way, I'm sure I'm not the only one who didn't realize what was being counted.

Watch the definitions, and have a fabulous Memorial Day weekend!


  1. That little detail (suicide vs. homicide) is one to catch anytime a statistic involving "death by gun" comes up.

    The CDC statistics quoted for Michigan are representative of stats for the U.S. as a whole. Typical stats for firearms-death have a small fraction as accidental, about 55% as suicide, and about 45% as homicide.

    Most organizations that want stricter laws about firearms will gladly quote "gun-death-stats" which ignore the distinction between homicide, suicide, and accident.

    I gained this knowledge by trying to bring stats to internet debates about firearms...

    1. Yes, I doubt I'll forget it now that I've seen it....but I certainly wouldn't have realized it if it hadn't been pointed out.

      It's interesting how many stats are like that...once you know the "secret" you can never look at them the same way.