Harvard researchers said a mass shooting occurs on average every 64 days, according to the Huffington Post. The average between 1982 and 2011 was every 200 days. Mass shootings have tripled since 2011.
The Huffington Post reported researchers defined the attacks as ones that "took place in public, in which the shooter and the victims generally were unrelated and unknown to each other, and in which the shooter murdered four or more people."
An FBI report last month stated the annual average of shootings per year between 2007 and 2013 as 16.4, while the yearly average between 2000 to 2006 was 6.4 shootings.
Northeastern University criminologist James Alan Fox uses a broader definition of mass shootings, according to the Huffington Post. His research included domestic shootings, like those in a home or gang-related killings.
Mother Jones' senior editor, Mark Follman, told the Huffington Post that the definitions are important and the differences need to be noted. "Our focus has been on public attacks as opposed to domestic attacks," Follman said. "Domestic killings are no less serious, but they are a different kind of problem. It's terrible when a mentally disturbed person slaughters his whole family in his home, but that's different from indiscriminate killing."
Mother Jones provided the data for the Harvard research, but was not a participant in the study.
Follman told the Huffington Post that he hopes the data will help law enforcement and law makers minimize shootings. "The universal goal is we want to prevent these from happening," said Follman. "You have to understand the problem better and track the problem accurately. The clearer the data we can get on mass shootings the better."
