http://www.cato.org/publications/commentary/gun-control-myths-realities
4. States that allow registered citizens to carry concealed weapons have lower crime rates than those that don’t.
True. The 31 states that have “shall issue” laws allowing private citizens to carry concealed weapons have, on average, a 24 percent lower violent crime rate, a 19 percent lower murder rate and a 39 percent lower robbery rate than states that forbid concealed weapons. In fact, the nine states with the lowest violent crime rates are all right-to-carry states. Remarkably, guns are used for self-defense more than 2 million times a year, three to five times the estimated number of violent crimes committed with guns.
Too lazy to look up... can you explain the diff between "shall issue" and "right to carry"?