It's not just a perception: Mass shootings have become more frequent, data shows

Uh... DUH!
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Mass shootings such as that carried out Wednesday night in Charleston, S.C., not only seem to have become more commonplace, but research shows they have become more frequent, and more deadly, over the last three decades.

Defining mass shootings as outbreaks of firearms violence in which four or more victims were killed and the shooter was unknown to most of his victims, researchers from Harvard University's School of Public Health and Northeastern University found that, in the roughly two-year period that ended in September 2013, a mass shooting occurred on average every 64 days. In the preceding 29 years, such shootings occurred on average every 200 days.

The shootings also claimed a heavier toll--a function, according to many experts, of guns' widening availability since the mid-20th century. Today, American civilians are thought to own as many as 310 million firearms. By one 2009 estimate, the number of guns per capita had doubled since 1968.

In street violence as in mass shootings, more powerful guns have also made a difference: A 1992 Archives of Surgery study tracked gunshot wounds between 1983 to 1990 in a busy hospital emergency room in Washington. Between 1988 and 1990 alone, researchers found, the mean number of gunshot entry wounds per patient rose from 1.44 to 2.04. The escalation of gunshot-wounds-per-patient was consistent, said researchers, with "a shift in weaponry toward high-capacity semi-automatic handguns," the authors wrote.

http://www.latimes.com/science/sciencenow/la-sci-sn-mass-shootings-more-frequent-data-20150618-story.html