It's only natural, faced with atrocities like those that took place in Aurora or Sandy Hook or Isla Vista, to sink into a "What the hell is wrong with the world?" attitude. And based on the conversations that often follow these tragedies, it would be easy to think that life in the United States is as dangerous as ever, that the country is an increasingly violent, brutal place. Luckily, the statistics tell a different story.
James Alan Fox, a criminologist at Northeastern University and frequent commentator on criminal justice issues, has kept a close eye on the numbers, tracking mass-shooting incidents with four or more fatalities between 1976 and 2012 — the most recent year for which FBI data are available. Data he provided Science of Us produced the following graph:
It's clear that there is no major upward trend. And slicing the data differently doesn't make a difference — Fox said that since homicides are on the downswing in general, the overall shape of the graph wouldn't change much if you changed the definition of a mass shooting to, say, three victims or more. There isn't even any upswing in the number of school shooting victims, at least based on the Department of Education's own official statistics (PDF).
Why, then, is there such a powerful feeling that things are getting worse? Media coverage plays a big role. It's almost hard to believe today, but there was a time in the not too distant past when people in New York might not even hear about a school shooting that happened across the country. Today, every incident immediately explodes onto the national stage and is then amplified a millionfold by social media. It's a visceral example of the availability heuristic — the easier it is for us to think of a certain type of event (whether a school shooting or a plane crash), the higher we rate its probability. But this is an illusion; just because it's easier than it ever has been to think of an example of a shooting doesn't mean these events are more likely than they were in the past.
All that said, the United States remains a very dangerous place by the standards of other developed countries (PDF), and little progress is being made on gun control, mental health, and other factors that contribute to the nation's higher-than-it-should-be homicide rate. But overall, things aren't getting worse by the year. To paraphrase Bill Clinton, trend lines are more important than headlines — or tweets or Facebook posts.
[Update: Owing to an editing error on my part, the graph we originally posted for this story was slightly off, and indicated higher numbers of incidents and victims than the data shows. The old, incorrect graph can still be viewed here, and an XLS sheet of Fox's data can be downloaded here.]