Warning: These researchers are refusing to release the data used in their already published study.

Public health researchers at Texas A&M University (Charles D. Phillips, Obioma Nwaiwu, Szu-hsuan Lin, Rachel Edwards, Sara Imanpour, and Robert Ohsfeldt) have a new piece in the Journal of Criminology that claims that concealed handgun permits have no statistically significant effect on crime rates. Depending on the regression reported, they look at data for either 3 or 4 states with permit data from 1998 to 2010 (Florida, Michigan, Pennsylvania, and Texas).

As past surveys of the literature have shown, there have been other studies that have found that right-to-carry laws don’t reduce violent crime, though they have been in the distinct minority. Yet, the worst that they can say is that these laws don’t produce a bad effect.

No serious explanation is offered for why these authors exclude other states or years? County level permit data are easily available for Illinois and Wisconsin because no permits were issued over this entire period of time. Oregon, Tennessee, North Carolina, and other states have county level data over this period of time. This is important because the test that they are preforming compares these states relative to one another during the period that they all have right-to-carry concealed handgun laws. When authors throw out data there had better be a good explanation for why they are doing it, but no explanation is offered here.