Complexity and Bounded Rationality in Individual Decision Problems Theodoros M. Diasakos Working Paper No. 90 December 2008 www.carloalberto.org THE CARLO ALBERTO NOTEBOOKS Complexity and Bounded Rationality in Individual Decision Problems¤ Theodoros M. Diasakosy December 2008z ¤I am grateful to Chris Shannon for invaluable advice on this and earlier versions. Discussions with David Ahn, Bob Anderson, Paolo Ghirardato, Shachar Kariv, Botond Koszegi, Matthew Rabin, Jacob Sagi, and Adam Szeidl were of signi¯cant bene¯t. I also received helpful comments from Art Boman, Zack Grossman, Kostis Hatzitaskos, Kristof Madarasz, George Petropoulos, Florence Neymotin, and participants in the Xth Spring Meeting of Young Economists, the 2005 Conference of the Southwestern Economic Association, the 3rd and 5th Conference on Research in Economic Theory and Econometrics, and the 2007 SAET conference. Needless to say, all errors are mine. This research was supported by a fellowship from the State Scholarship Foundation of Greece. yCollegio Carlo Alberto E-mail:
[email protected] Tel:+39-011-6705270 z°c 2008 by Theodoros M. Diasakos. Any opinions expressed here are the author's, not of the CCA. Abstract I develop a model of endogenous bounded rationality due to search costs, arising implicitly from the decision problem's complexity. The decision maker is not required to know the entire structure of the problem when making choices. She can think ahead, through costly search, to reveal more of its details. However, the costs of search are not assumed exogenously; they are inferred from revealed preferences through choices. Thus, bounded rationality and its extent emerge endogenously: as problems become simpler or as the bene¯ts of deeper search become larger relative to its costs, the choices more closely resemble those of a rational agent.