It also appears, at least from the press release (the article is behind a very expensive pay wall), that "violent crime" is distinguished from "violent gun crime". So they count crimes where a criminal uses a gun in homicides, rapes, robbery, aggravated assault, but not the crimes in the same categories where the criminal, or multiple criminals, used a knife, baseball bat, pipe, screwdriver, fists, etc., as if no one would need or want to use a firearm to protect themselves unless their attacker(s) had a gun. A "reasonable belief in imminent grievous bodily injury" isn't limited to the attacker having a "gun", obviously. Well, obvious I guess to anyone except the "researchers" accumulating these statistics.