Study on Background Checks

Between January 1, 2009 and July 31, 2015, there were 37 mass shootings in states where background checks were required for all handgun sales and 96 mass shootings in states where they were not. Controlling for population, there were 52 percent fewer mass shootings in states that require background checks for all handgun sales than in states that do not.

The difference was more pronounced among shootings committed by prohibited people. During the period of observation, there were 44 mass shootings committed by assailants known to be prohibited from possessing firearms—10 in states that require background checks for all handgun sales and 34 in states that do not. Controlling for population, there were 63 percent fewer mass shootings committed by people prohibited from possessing firearms in states that require background checks for all handgun sales than in those that do not.