This is OPPOSITE the advice in found at
http://en.wikipedia.org/wiki/The_Wisdom_of_Crowds
unless you limit your crowds to be the "talking head stock experts on TV"....booohyaaaa
Actually there's no conflict at all.
The key concept in the Wisdom of Crowds is that each person provides their input independently of other people (as in the case of guessing the weight of the ox at the fair). Dreman discusses how the situation changes when you allow the people to interact together.
IOW - at the county fair, if everyone writes their guess on the slip and walks away, you get a good answer.
Alternatively, you could ask everyone who wants to submit a guess to go in a room with everyone else, talk it over, and then submit their guesses. If you do that, the accuracy of the estimate goes way down. It has everything to do with the dynamics of groups and our social human nature.
One of the critical aspects of
The Delphi Method, for example, is never allowing the experts you've assembled to ever interact, ensuring that the participants are anonymous, and sanitizing information provided between sessions so that no one knows what information was provided by any other participants.
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The stock market is inefficient because people look to experts instead of deciding independently.
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When you want to solve a problem, the last thing you should ever do is put a bunch of experts in a room and have them come up with a recommendation. Doing something such as that on global warming guarantees two things; you will get good publicity and the resulting conclusions and recommendations will almost assuredly have serious errors.
Getting back to real estate, for example, the time to buy real estate is when all of the pundits are saying that real estate is the worst possible place to put your money. The time to sell is when everyone thinks the sky is the limit for real estate. If you blindly follow the crowd, trusting in its wisdom, you will end up buying high and selling low.