If the United States had a Virginia-Tech-sized massacre every single year, how much would that increase the homicide rate? And how much would preventing a similar massacre every year reduce it?
The homicide rate is usually measured in persons per 100,000 population. The U.S. annual homicide rate has hovered around 6 per 100,000 for the last several years. There are approximately 300 million people in the U.S. That means an additional 32 homicides per year (the VT death toll) would increase the homicide rate by about 0.01 per 100,000. Likewise, if we succeeded in eliminating one VT-sized massacre per year, we would reduce the homicide rate by about 0.01 per 100,000. Hardly a blip, and well within the year-to-year variation in the homicide rate.
The effect would be exactly the same if 32 states each had one more (or one fewer) homicides per year. If that happened, nobody would even notice.
We could look only at the state of Virginia, of course. Another VT-sized massacre each year would raise Virginia’s homicide rate by about 0.4 per 100,000. Now that’s more significant, though still within the state’s year-to-year variation. If we looked only at the population of VT, the homicide rate would be obscenely higher. But these numbers aren’t as meaningful as the national number, because spree killings aren’t concentrated like that. The last spree killing was not in Virginia, and the next one probably won’t be either.
In short, what makes the massacre at VT, or any other spree killing, so vivid is that it happened all at once, all in one location. Availability bias makes us interpret such an event as indicative of a major problem. Any “solution” for spree killings – whether implementing tougher gun controls or replacing gun-free zones with concealed-carry permits – would have a negligible impact unless it also affected everyday, run-of-the-mill homicides.
This should go without saying, but I’ll say it anyway: none of this is meant to minimize the grief of the Virginia Tech community, or of the family and friends of the victims. It is simply meant to put the event into perspective.