When asked to name the attributes of someone who is particularly bad at predicting, Tetlock needed just one word. "Dogmatism," he says. That is, an unshakable belief they know something to be true even when they don't. Tetlock and other scholars who have tracked prominent pundits find that they tend to be "massively overconfident," in Tetlock's words, even when their predictions prove stone-cold wrong. That is a lethal combination - cocky plus wrong - especially when a more prudent option exists: simply admit that the future is far less knowable than you think.
Unfortunately, this rarely happens. Smart people love to make smart-sounding predictions, no matter how wrong they may turn out to be. This phenomenon was beautifully captured in a 1998 article for Red Herring magazine called "Why Most Economists' Predictions Are Wrong." It was written by Paul Krugman, himself an economist, who went on to win the Nobel Prize. Krugman points out that too many economists' predictions fail because they overestimate the impact of future technologies, and then he makes a few predictions of his own. Here's one: "The growth of the Internet will slow drastically, as the flaw in 'Metcalfe's law' - which states that the number of potential connections in a network is proportional to the square of the number of participants - becomes apparent: most people have nothing to say to each other! By 2005 or so, it will become clear that the Internet's impact on the economy has been no greater than that fax machine's."
-as excerpted from Levitt and Dubner's Think Like A Freak