Reprinted, with permission, from the July 1989 issue of Reason Magazine. What they reveal is suggestive, but what they conceal is vital. The problem is demonstrated by the most recent entry in a long line of scientific research purporting to show a causal link between gun availability and homicide. The second step in their reasoning seems indisputable.
Homicide is definitely more common in Seattle.
The authors present a believable although not entirely accurate case to support the notion, as claimed in the third step of their reasoning, that Vancouver's handgun regulations are much more stringent. We are therefore being asked, at the conclusion of the study, to believe that a difference in gun availability explains the difference in homicide rates when a difference in gun availability has not itself been established. Indeed, the situation is even more troublesome. Differences between the two cities in the permit regulations render these two numbers strictly noncomparable. Cook's index however, does not measure the relative prevalence of gun ownership in various cities.