Tim Lambert (deltoidblog AT gmail.com) is a computer scientist at the University of New South Wales.
brian.m.leary said:
In the five months after the passage of the mandatory gun ownership law in Kennesaw, Georgia the residential burglary rate was down 89% from the same period the year before. Does this prove the law worked? No - proof is difficult in these matters.
However, is it clear that the law had no effect? Hardly.
The source for this claim appears to be Kleck's paper in "Social Problems" v35p15, where he states there were five reported residential burglaries in the seven months after the law, while there were 45 in the corresponding seven months of the preceding year.
As you have noted, this isn't enough data to conclude if the law did or did not have an effect. Sure, there is a big reduction, but how do we know that before year was not unusually high?
If the sequence is 7 43 4 5 6 45 5
we certainly wouldn't conclude that the law caused the reduction.
However, there is a MUCH more serious problem with this 89% reduction claim. From the "Criminology" v29p541 paper by McDowall et al (which provides monthly totals) I computed the total number of burglaries in the seven months after the law (23) and for the seven corresponding months of the previous year (37). Something is wrong here. It's possible that 5 out of 23 burglaries after the law were residential but it sure as hell ain't possible for 45 out of 37 burglaries before to be residential. One dataset must be wrong.
McDowall et al's data come from the FBI's Uniform Crime Reports. Kleck's data comes from a telephone conversation somebody else had with the Kennesaw police chief.
I think the UCR data is likely to more accurate.
