The CDC has published a technically true — but profoundly misleading — statistic about the chance of outdoor infection. The story is brought to us by New York Times journalist David Leonhardt in his daily, “The Morning Newletter”:
When the Centers for Disease Control and Prevention released new guidelines last month for mask wearing, it announced that “less than 10 percent” of Covid-19 transmission was occurring outdoors. Media organizations repeated the statistic, and it quickly became a standard description of the frequency of outdoor transmission.
So, what’s the actual number?
The number is almost certainly misleading. It appears to be based partly on a misclassification of some Covid transmission that actually took place in enclosed spaces (as I explain below). An even bigger issue is the extreme caution of C.D.C. officials, who picked a benchmark — 10 percent — so high that nobody could reasonably dispute it.