Scandinavian Working Papers in Economics

SSE/EFI Working Paper Series in Economics and Finance,
Stockholm School of Economics

No 535: Confidence Interval Estimation Tasks and the Economics of Overconfidence

David Cesarini (), Örjan Sandewall () and Magnus Johannesson ()
Additional contact information
David Cesarini: Department of Economics, London School of Economics, Postal: Houghton Street, London WC2A 2AE, United Kingdom
Örjan Sandewall: Department of Economics, London School of Economics, Postal: Houghton Street, London WC2A 2AE, United Kingdom
Magnus Johannesson: Dept. of Economics, Stockholm School of Economics, Postal: P.O. Box 6501, SE-113 83 Stockholm, Sweden

Abstract: Experiments in psychology, where subjects estimate confidence intervals to a series of factual questions, have shown that individuals report far too narrow intervals. This has been interpreted as evidence of overconfidence in the preciseness of knowledge, a potentially serious violation of the rationality assumption in economics. Following these results a growing literature in economics has incorporated overconfidence in models of, for instance, financial markets. In this paper we investigate the robustness of results from confidence interval estimation tasks with respect to a number of manipulations: frequency assessments, peer frequency assessments, iteration, and monetary incentives. Our results suggest that a large share of the overconfidence in interval estimation tasks is an artifact of the response format. Using frequencies and monetary incentives reduces the measured overconfidence in the confidence interval method by about 65%. The results are consistent with the notion that subjects have a deep aversion to setting broad confidence intervals, a reluctance that we attribute to a socially rational trade-off between informativeness and accuracy.

Keywords: overconfidence; uncertainty; monetary incentives; experiments

JEL-codes: C91; D80; Z13

35 pages, September 22, 2003

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