(March 1) -- When it comes to mass public shootings, the decade doesn't seem to be starting out too well. Just two months in and already there was a shooting rampage in rural Virginia (which claimed eight lives), one at the University of Alabama (three dead) and other in Denver, near Columbine High School, in which two middle school students were injured. But the fact is that, while mass public shootings always tend to galvanize massive media coverage, they are becoming increasingly less common, falling sharply in the last decade compared with the previous two. And understanding this decline is...