Jill Lepore wrote, “One study suggests that two-thirds of Americans between the ages of fifteen and thirty-four who were treated in emergency rooms suffered from injuries inflicted by police and security guards, about as many people as the number of pedestrians injured by motor vehicles.” In fact, the actual percentage is not 66% but something closer to 0.2%.

Estimate subject to further correction, of course, but there’s no question that Lepore misread the relevant study and misread it very badly indeed. The sentence I quoted has now been changed, with an acknowledgement of error at the bottom of the article.

The interesting thing to me here is that Lepore seems not to have been skeptical about what anyone who thought about the matter for two seconds would surely have seen as a bizarrely high number. I’ve been an American “between the ages of fifteen and thirty-four who were treated in emergency rooms,” indeed this happened to me several times, and in every case except one I was there because of a sports injury. Two broken arms, a badly sprained ankle, a couple of dislocated or broken fingers, an eye that had had someone else’s finger jammed into it … these are my emergency room stories, and they are very common indeed. (The one exception was a car accident that left me with whiplash.) Then there are the young people who have bicycle or motorcycle crashes, falls while drunk, accidents at work, appendicitis attacks … and Jill Lepore, one of our most distinguished historians, thought it was perfectly plausible that if you took every single one of those causes of ER visits, plus every other cause of an ER visit, and then doubled them — you’d have the number of ER visits for “injuries inflicted by police and security guards.”

How could Lepore ever have thought that was plausible? I can only think of one explanation: Because she unconsciously assumed that what she reads in the papers, what she sees on TV, what gets tweeted about on Twitter, is not only important but proportionately representative of what happens in the world. Maybe there’s a lesson here for all of us.