Is Lott right? We don’t know. His work is more sophisticated than most older studies cited to support gun control. Yet large observational studies have many potential weaknesses, especially when they look for trends over time. Lots of things happen in 18 years, not all of which are in Lott’s model—for example, police have become more aggressive in seizing illegal guns. Good data are hard to come by—for example, the number of people carrying guns legally is lower than the number of permits issued and is hard to estimate accurately. It would take very detailed study to reach an informed opinion on Lott’s statistics.
The best reason to question Lott’s findings combines awareness of the weaknesses of observational studies with the fact that statistical studies with stronger designs support reducing the presence of guns. Temporary bans on carrying guns in several cities in Colombia—highly publicized and enforced by police checkpoints and searches—reduced murder rates. The Kansas City Gun Experiment compared two high-crime areas. In one, police seized guns by searches during traffic stops and after minor offenses. Gun crimes dropped by half in the treatment area and were unchanged in the control area. There seems good reason to think that reducing illegal carrying of guns reduces gun crime. Lott, of course, argues for legal carrying. This distinction between legal and illegal carrying of guns makes it possible for both Lott and some of his critics to be right. Lower illegal gun carrying may reduce crime. Higher legal gun carrying could also reduce crime. Like many questions of causation, this one remains open.