According to health researcher Etienne Krug, the homicide rate in the United States is six times higher than that of other developed nations. And though the rate varies from year to year, according to the FBI, in the United States guns are used in about 70 percent of homicides. One of the main tenets of America’s gun control movement is that reducing the availability of guns would reduce crime.

Of course, progun groups such as the National Rifle Association reject this claim. On the contrary, they argue the opposite—that private ownership of handguns actually reduces crime rates. This argument received nationwide attention in 1998 with the publication of economist John R. Lott Jr.’s book More Guns, Less Crime. In the book, Lott uses detailed statistical analysis of crime data to support the view, long embraced by gun advocates...