Nate Silver (who runs the NYT Political Polling site FiveThirtyEight) has a new book about the difficulties faced when trying to predict future events. The NYT has an excerpt – in this case, about weather forecasting.
Catering to the demands of viewers can mean intentionally running the risk of making forecasts less accurate. For many years, the Weather Channel avoided forecasting an exact 50 percent chance of rain, which might seem wishy-washy to consumers. Instead, it rounded up to 60 or down to 40. In what may be the worst-kept secret in the business, numerous commercial weather forecasts are also biased toward forecasting more precipitation than will actually occur. (In the business, this is known as the wet bias.) For years, when the Weather Channel said there was a 20 percent chance of rain, it actually rained only about 5 percent of the time.
The Weatherman Is Not a Moron [NYT]