> Jordan Hayes:
>
> >I'd be interested in your opinion of criminologists like Don Kates
> and
> >Gary Kleck, especially Kleck
>
> oh yes, Gary Kleck, who amused other criminologists a few years back
> with his claim that 2.5 million crimes were prevented through defensive
> gun uses each year. Among other things, he had 322,000 rapes prevented
> through gun use (as against 316,000 reported rapes; are the majority of
> rapists fended off by gun-wielding victims?) and 130,000 criminals
> wounded or killed by defensive gun use each year; the *total* number of
> nonfatal shootings known to police is about 100,000.
>
> You can find a nice demolition job of his study by Philip Cook and Jens
> Ludwig at http://www.ncjrs.org/pdffiles/165476.pdf. When they're
> through, there's not much left standing.
There's also a text file version at http://www.ncjrs.org/txtfiles/165476.txt
MAJOR POINT: Kleck's methodology was seriously flawed, counting a large number of false positives. (In relatively rare events, the preponderance of false negatives is far smaller than false positives, since the underlying condition -- positive occurance -- is much rarer. Thus even if people err in both directions equally often the false positives statistically overwhelm false negatives.)
Cook & Ludwig explain that there are plausible reasons why a greater number of false positives might be reported (beyond simply random error):
"Respondents might falsely provide a positive response to the DGU question for any of a number of reasons:
o "They may want to impress the interviewer by their heroism and hence exaggerate a trivial event.
o "They may be genuinely confused due to substance abuse, mental illness, or simply less-than-accurate memories.
o "They may actually have used a gun defensively within the last couple of years but falsely report it as occurring in the previous year--a phenomenon known as 'telescoping.'
"Of course, it is easy to imagine the reasons why that rare respondent who actually did use a gun defensively within the time frame may have decided not to report it to the interviewer. But again, the arithmetic dictates that the false positives will likely predominate."
To avoid these problems, Cook & Ludwig minimized false positives by first asking if people have been victims of a crime. Kleck & Gertz (his associate in the study he relies on) failed to do this.
In addition to the points Josh cites, they note that nearly 1/3 of repondents "indicated that the circumstance of the DGU [defensive gun use] was rape, robbery, or attack--but then responded 'no' to a subsequent question: 'Did the perpetrator threaten, attack, or injure you?'"
They then go on to say:
"The key explanation for the difference between the 108,000 NCVS estimate for the annual number of DGUs and the several million from the surveys discussed earlier is that NCVS avoids the false-positive problem by limiting DGU questions to persons who first reported that they were crime victims. Most NCVS respondents never have a chance to answer the DGU question, falsely or otherwise."
It should be noted that Kleck's survey is one of the most highly-touted by the gun nuts. It's their idea of real first-rate science.
-- Paul Rosenberg Reason and Democracy rad at gte.net
"Let's put the information BACK into the information age!"