Division of the Humanities and Social Sciences California Institute of Technology Pasadena, California 91125 Information Aggregation in Double Auctions: Rational Expectations and the Winner's Curse

This paper inquires about the ability of double auction institutions to aggregate information in the context of a " common value " information structure that is known to produce the winner's curse in sealed bid environments. While many fundamental features of the economic environment are different from those studied in the context of sealed bids, the pattern of information distributed to the population of traders is the same. This gives us an opportunity to determine if the behaviors reported in sealed bid environments can be detected in the more active market environment. As such the experiments are also a test of the robustness of earlier experiments that demonstrate that in economies with homogeneous preferences similarities single compound securities organized by double auctions are able to aggregate information. The basic result is that a severe winner's curse is not observed. The irrationality observed in sealed bids does not extend itself to the double auction environment. Information aggregation is observed and the rational expectations model receives support.