were 25 mass shooting in America. In around the same number of years, from Columbine until Last Vegas there have been 78. The country as a whole has been getting safer since 1982. The big thing that changed is the media coverage and I believe Columbine was the start of that level of coverage.
Using this data:
https://docs.google.com/spreadsheets/d/1XV4mZi3gYDgwx5PrLwqqHTUlHkwkV-6uy_yeJh3X46o/pub?output=html&widget=false#Edited by tgr at 14:32:52 on 10/04/17