Article by Ray Fisman, Andrew Gelman, and Matthew C. Stephenson: “This winter, the university where one of us works sent out an email urging employees to wear a hat on particularly cold days because “most body heat is lost through the top of the head.” Many people we know have childhood memories of a specific figure—perhaps 50 percent or, by some accounts, 80 percent of the heat you lose is through your head. But neither figure is scientific: One is flawed, and the other is patently wrong. A 2004 New York Times column debunking the claim traced its origin to a U.S. military study from the 1950s in which people dressed in neck-high Arctic-survival suits were sent out into the cold. Participants lost about half of their heat through the only part of their body that was exposed to the elements. Exaggeration by generations of parents got us up to 80 percent. (According to a hypothermia expert cited by the Times, a more accurate figure is 10 percent.)
This rather trivial piece of medical folklore is an example of a more serious problem: Through endless repetition, numbers of dubious origin take on the veneer of scientific fact, in many cases in the context of vital public-policy debates. Unreliable numbers are always just an internet search away, and serious people and institutions depend on and repeat seemingly precise quantitative measurements that turn out to have no reliable support…(More)”.