In a remarkable paper published in 1997, John Lott and David Mustard managed to set the agenda for much subsequent dataset work on the impact of guns on crime in America by creating a massive dataset of crime across all U.S. counties from 1977 through 1992 and by amassing a powerful statistical argument that state laws enabling citizens to carry concealed handguns had reduced crime. The initial paper was followed a year later by an even more comprehensive and sustained argument to the same effect in a book solely authored by John Lott entitled More Guns, Less Crime (now in its second edition). The work by Lott and Mustard has triggered an unusually large set of academic responses, with talented scholars lining up on both sides of the debate. Indeed, a panel of the National Academy of Sciences has been convened to sort through the now large body of conflicting studies.