The congressional shootings Wednesday prompted some Republicans to call for lawmakers to be armed. Would that be a good idea—more guns, less crime? Not necessarily.

House Majority Whip Steve Scalise of Louisiana remained in critical condition after surgery to treat a gunshot wound to the hip. The attack in a Washington suburb by an apparently politically motivated shooter using a military-style, large-capacity rifle also left three others wounded. On the same day, on the other side of the nation, a man shot five co-workers—three of them fatally—at a United Parcel Service facility in San Francisco.

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So who’s right? The best research I’ve seen came from law professors Ian Ayres of Yale and John Donohue III of Stanford. In a 2003 paper entitled, “Shooting Down the ‘More Guns, Less Crime’ Hypothesis,” they offer a nuanced assessment that hasn’t been improved on since. Their conclusion: “We find that the statistical evidence that these laws have reduced crime is limited, sporadic, and extraordinarily fragile.”

Examined closely, the data simply don’t support Lott’s theory. For example, Ayres and Donohue point out, Lott overlooks the strong association of permissive concealed-carry laws with rising incidences of robbery and various types of property crime. Those increases “are not consistent with any plausible theory of deterrence” by permissive gun laws, they convincingly assert.

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Ayres and Donohue do acknowledge that Lott got at least one thing right: Permissive firearm laws “have not led to the massive bloodbath of death and injury that some of their opponents feared.”