A new study by Adam Lankford, of the University of Alabama, which will be presented next week at the annual conference of the American Sociological Association, shows a strong correlation between the availability of guns and the prevalence of gun massacres. With the same certainty that David Hemenway's work established the link between the number of guns in a society and the number of gun killings, we now know that there is a correlation between the availability of guns and the major public assaults that have been a part of American life since Columbine.