"Judging from the large volume of trade in the financial markets and the astounding volatility of prices, one has to accept the idea that investors hold divergent and fast fluctuating beliefs. For this to make sense, I see only two possible hypotheses. Both individual and professional investors

"Judging from the large volume of trade in the financial markets and the astounding volatility of prices, one has to accept the idea that investors hold divergent and fast fluctuating beliefs. For this to make sense, I see only two possible hypotheses. Both individual and professional investors receive a lot of information – some of it public but a lot more of it private – on which they act. Or they all receive similar information but each one interprets that information somewhat differently from the other. Although it is not quite rational, I find the latter behaviour more plausible than the former. A large part of the second edition of A Behavioral Approach to Asset Pricing is devoted to developing this arresting, although by no means mainstream, hypothesis. In that endeavour, Professor Shefrin is a maverick and a pioneer. "

Bernard Dumas, Professor of Finance, Swiss Finance Institute, Universite de Lausanne, Switzerland