Simultaneous Over- and Underconfidence : Evidence from Experimental Asset Markets

In this paper we investigate individual overconfidence within the context of an experimental asset market. Overall, 72 participants traded one risky asset on six markets of 12 participants each. Our results indicate that participants are not generally prone to overconfidence. A comparison of two different measures of overconfidence, (i) subjective confidence intervals and (ii) differences between objective accuracy and subjective certainty, lead to a different classification of behavior in our data-set. We observe well-calibration as well as over- and underconfidence