The Signal and the Noise: Why So Many Predictions Fail-but Some Don't

by Nate Silver

H1N1 had been responsible for the worst pandemic in modern history: the Spanish flu of 1918–20, which afflicted a third of humanity and killed 50 million,3 including 675,000 in the United States. For reasons of both science and superstition, the disclosure sent a chill through the nation’s epidemiological community. The 1918 outbreak’s earliest manifestations had also come at a military base, Fort Riley in Kansas, where soldiers were busy preparing to enter World War I.4 Moreover, there was a belief at that time—based on somewhat flimsy scientific evidence—that a major flu epidemic manifested itself roughly once every ten years.5 The flu had been severe in 1938, 1947, 1957, and 1968;6 in 1976, the world seemed due for the next major pandemic. A series of dire predictions soon followed. The concern was not an immediate outbreak—by the time the CDC had positively identified the H1N1 strain, flu season had already run its course. But scientists feared that it foreshadowed something much worse the following winter. There had never been a case, a prominent doctor noted to the New York Times,7 in which a newly identified strain of the flu had failed to outcompete its rivals and become the global hegemon: wimpy A/Victoria stood no chance against its more virulent and ingenious rival. And if H1N1 were anywhere near as deadly as the 1918 version had been, the consequences might be very bad indeed. Gerald Ford’s secretary of health, F. David Mathews, predicted that one million Ameri...