The map and the database behind it is from Mother Jones magazine. They first published this in 2012 when there were 62 such incidents in the 30 years between 1982 and 2012. Since January 2013 there have been 53 more. There are other similar databases out there, however they believe theirs is most conservative.
The criteria they used for a mass shooting was the FBI definition of a mass shooting as a single attack in a public place in which four or more victims were killed. That criteria was changed by Obama in 2013 to three or more victims killed. So it may be hard for some to say those shootings are increasing in the last six years and 11 months. But in my non-statistical mind it seems pretty obvious that they are. 62 in 30 years averages about one every six months. 53 in almost seven years averages closer to one every six weeks. Although I concede that the frequency cannot be accurately mapped due to the different data criteria. Although it seems the more recent ones definitely had many more than three victims, and only 16 out of 53 had three fatalities.
At first glance I also wondered about the zero mass shootings in the states of Idaho, Montana, Wyoming, both Dakotas, the three upper tier New England states, and Alaska. Probably that is a factor of their less diverse populations. But maybe less stress and a more laid back lifestyle in the country applies also. Or something else entirely?
Here is a link to the updated article:
https://www.motherjones.com/politics/2012/07/mass-shootings-map/
