Eugene poses this question in his last post, and asks whether the rate of such incidents has increased. The answers are "very rare," and "probably not." In her 2004 book Rampage: The Social Roots of School Shootings (pg. 51), Harvard Professor Katherine Newman notes that there was no more than one such case in the entire US for any year between the 1974-1975 and 1991-92 school years. There was a small spike in the 1990s (starting with 2 cases in 1993, and a high of 6 in 1997-98), but falling again to 1 case in 1999-2000 and 0 in 2001-2002. It is likely that there was a brief 1990s spike caused by copycats imitating a few highly publicized cases, such as Columbine. At the same time, the peak years still had such low absolute numbers of cases that it is quite possible that the increase was simply a result of random chance variation. I don't have comparable statistics on mass shootings on university campuses. But such cases are likely to be even more uncommon than those in schools, given that the total number of murders occurring on college campuses nationwide tends to be about 10 to 20 per year (as noted in my last post). The extreme rarity of such incidents should be kept in mind as we decide what, if any, policy changes should be made in response to the Virginia Tech tragedy. Some changes may well be warranted, but we should guard against costly overreactions such as the draconian "zero tolerance" policies implemented in many schools after the Columbine attacks in 1999. As a professor in the Virginia state university system (of which Virginia Tech is a part), I hope we can resist the temptation to enact similar measures.