Deltoid

The actual number is 34%, as I stated above. The survey didn’t ask how many times it had happened. An average of two for those that had been thwarted is my guess based on assuming that the distribution of the number of thwartings was Poisson (ie, each criminal was equally likely to encounter an armed victim).

jmaraldo writes:

I have not had the pleasure of making Mr. Poisson’s acquaintance - ie, I know nothing of statistical methods :=) But why does he suppose that the likelihood of encounter with an armed victim is equal for all criminals though criminals choose the type of crime in which they will engage?

Because, it makes the calculations simpler :-). Of course, it’s only an approximation. A quick simulation reveals that even if the risk differs greatly for different criminals, so that 80% of the DGUs are against 20% of the criminals, the average number of encounters for those criminals that had at least one would be three. This amounts to a 50% increase in the estimate of DGUs to about 100k.

And on a slightly different subject, aren’t we comparing apples and oranges when we compare the response of convicts to the response of citizens at large? Why assume that convicts’ experience of meeting armed resistance is representative of the experience of criminals generally, when the convicts comprise a (very small) subset of the nation’s criminal population? Wouldn’t a random sampling of civilians be more representative of the general population’s experience of armed defense than a random sampling of convicts?

Other things being equal, yes. However, it seems unlikely that errors introduced by using a somewhat biased samples will not be that great. (If DGU makes it more likely for a criminal to be caught, then the bias will cause an OVERestimate.)

I don’t see how we can explain the enormous disparity in the estimates by sample bias. Some people must not be telling the truth. Generally we would expect non-criminals to more honest, but the choice is between most of the criminals lying, and 3% of the general population lying.

In any case, Kleck is clearly wrong when he cites the 34% statistic as being supportive of his result. Without exception, every single crosscheck I have been able to carry out indicates that his estimate is way too high.

Paul Blackman wrote:

“Just a reminder that Pim’s reliance upon Killias for showing a relationship between gun ownership and homicide is undermined by Kleck’s critique of Killias for some deliberate distortions of data, inappropriate exclusions of some countries versus others, etc. Pim doesn’t accept Kleck’s refutation, and it seems pointless to recount it, but Kleck would find the data unimpressive.”

At the heart of Kleck’s “refutation” is a statistical error that a first year undergraduate should not make. I am surprised that someone with Dr Blackman’s undoubted skills did not notice. Kleck computed the Pearson correlation coefficient without first excluding outliers.

Anyway, I note that Killias has repeated the study using the additional data obtained in the 1992 International Crime Survey.

He obtained similar results as before: Household gun ownership was associated with more gun homicides and gun suicides, and not associated with non-gun homicides or suicides.

JB:

Gun-control proponents of some stature (e.g., Wolfgang and Cook) have reluctantly acknowledged the quality of Kleck’s survey methodology

Sorry, but Cook does have some problems with Kleck’s methodology:

“The Gun Debate’s New Mythical Number: How Many Defensive Gun Uses Per Year?” Journal of Policy Analysis and Management Spring 1997

Philip J. Cook, David Hemenway, and Jens Ludwig

In recent years the self-defense uses of personal firearms has become a central issue in the debate over gun control. A widely noted estimate, based on a national survey, is that guns are used in legitimate self-defense over 2.5 million times per year — far more often than they are used in crime. Several subsequent surveys have found similar results on the volume of self- defense uses. We analyze these results, demonstrating that some of the respondents who report self-defense uses must be mistaken, and suggesting several reasons why these “false positives” might arise. More generally we argue that any screening method applied to the general population method to measure the prevalence of a rare event (such as self-defense with a gun) will tend to generate more false positives than false negatives. This fact is accommodated in medical screening methods but usually ignored in the methodology of social surveys. Further, it is not at all clear that “more is better” when it comes to defensive gun uses.

“Stephen Heyer” writes:

When confronted with the fact that “In the last 16 years the number of guns owned in Australia has quadrupled. The number of firearm deaths have dropped by 46% in that period and guns are being used less in crime.”

What bothers me is that this bogus “fact” has been repeated several times and nobody has noticed how wildly incorrect it is.

I looked in the reference you cite: “How Firearm Crime is Declining”

It claims that the number of firearms owned in Australia has increased from about 2.5 million to about 4 million (Graph 1). I do not believe that “quadrupled” is the appropriate way to describe this increase.

In any case, the number of guns around is not a measure of the rate of lawful gun ownership. As far as gun ownership rates go this appears to have declined along with the firearm homicide rate. According to the 1975 General Social Survey 25% of Australian households possessed firearms, while the 1989 International Crime Survey got a figure of 20%. It doesn’t necessarily follow that the decline in gun ownership caused the decline in gun homicides, put it’s certainly possible.

With the exception of the most psychopathic, people automatically adjust their level of force so that they achieve their desired outcome with whatever means they use. If they do not intend to kill, and are using a gun, then they will be careful not to kill with the gun. If they intend to kill, and only have a knife, they will just try a bit harder.

Really? So how come assaults with large calibre guns have larger fatality rates than with assaults with small calibre guns? Are you seriously suggesting that someone who shoots someone with a 22 believes that it has no chance of killing?