The full title of the paper is “More Guns, More Unintended Consequences: The Effects of Right-to-Carry on Criminal Behavior and Policing in US Cities” and the authors are John J. Donohue, Samuel V. Cai, Matthew V. Bondy, and Philip J. Cook (does Cook get enough credit for his trajectory of ongoing productivity?) and here is the abstract:
We analyze a sample of 47 major US cities to illuminate the mechanisms that lead Right-to-Carry concealed handgun laws to increase crime. The altered behavior of permit holders, career criminals, and the police combine to generate 29 and 32 percent increases in firearm violent crime and firearm robbery respectively. The increasing firearm violence is facilitated by a massive 35 percent increase in gun theft (p=0.06), with further crime stimulus flowing from diminished police effectiveness, as reflected in a 13 percent decline in violent crime clearance rates (p=0.03). Any crime-inhibiting benefits from increased gun carrying are swamped by the crime-stimulating impacts.
Here is the link to the NBER working paper.