University of California at Berkeley psychologist Philip Tetlockmade an experimental project.

He picked 284 people who made their living "commenting or offering advice on political and economic trends" and began asking
them to make predictions about future events. He had a long list of pertinent questions. Would George Bush be reelected? Would
there be a peaceful end to apartheid in South Africa? Would Quebec secede from Canada? Would the dot-com bubble burst?
In each case, the pundits were asked to rate the probability of several possible outcomes. Tetlock then interrogated the pundits
about their thought processes so he could better understand how they'd made up their minds. By the end of the study, Tetlock had
quantified 82,361 different predictions.

After Tetlock tallied the data, the predictive failures of the pundits became obvious. Although they were paid for their keen
insights into world affairs, they tended to perform worse than random chance. Most of Tetlock's questions had three possible
answers; on average, the pundits had selected the right answer less than 33 percent of the time. In other words, a dart-thro wing chimp would have beaten the vast majority of professionals. Tetlock also found that the most famous pundits in his study tended to be the least accurate, consistently churning out overblown and overconfident forecasts. Eminence was a handicap.

From: How We Decide by Jonah Lehrer
http://www.amazon.com/How-We-Decide-Jonah-Lehrer/dp/0547247990/ref=sr_1_1?ie=UTF8&qid=1315645820&sr=8-1