The efficiency of financial markets and their potential to produce bubbles are central topics in academic and professional debates. Yet, little is known about the contribution of financial professionals to price efficiency. We run 116 experimental markets with 412 professionals and 502 students. We find that professional markets with bubble drivers – capital inflows or high initial capital supply – are susceptible to bubbles, although they are more efficient than student markets. In mixed markets with students, bubbles also occur, but professionals act as price stabilizers. We show that heterogeneous price beliefs drive overpricing, especially in bubble-prone market environments. Authors have furnished an Internet Appendix, which is available on the Oxford University Press Web site next to the link to the final published paper online.

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. shorter, bubbles than markets with symmetrically informed or uninformed traders. Hence, fundamental values are better reflected in market prices -implying higher market efficiencywhen some traders know more than others about the future prospects of an asset. We also find that asymmetric information has a similar abating impact on bubbles as when uninformed traders accumulate experience, though for different reasons. Terms of use: Documents in EconStor may

We define and examine three minimal market games (sell-all, buy-sell, and double auction) in the laboratory relative to the predictions of theory. These closed exchange economies have some cash to facilitate transactions, and include feedback. The experiment reveals that (1) the competitive general equilibrium (CGE) and noncooperative (NCE) models are reasonable anchors to locate most but not all the observed outcomes of the three market mechanisms; (2) outcomes tend to get closer to CGE predictions as the number of players increases; (3) prices and allocations in double auctions deviate persistently from CGE predictions; (4) the outcome paths across the three market mechanisms differ significantly and persistently; (5) importance of market structures for outcomes is reinforced by algorithmic trader simulations; and (6) none of the three markets dominates the others across six measures of performance. Inclusion of some mechanism differences into theory may enhance our understanding of important aspects of markets. 1 We thank Benjamin Felt and Ryan Dunn for their assistance with the laboratory experiments. We also thank two anonymous referees and the editor for very helpful comments and suggestions that greatly improved the paper. Financial support by the Austrian Forschungsfoerderungsfonds (FWF, grant P-20609) is gratefully acknowledged.

Market Design and Moral Behavior *In an experiment with 739 subjects we study whether and how different interventions might have an influence on the degree of moral behavior when subjects make decisions that can generate negative externalities on uninvolved parties. Particularly, subjects can either take money for themselves or donate it to UNICEF for measles vaccines. By considering two fairly different institutional regimes -one with individual decision making, one with a doubleauction market -we expose the different interventions to a kind of robustness check. We find that the threat of monetary punishment promotes moral behavior in both regimes. Getting subjects more involved with the traded good has no effect, though, in both regimes. Only the removal of anonymity, thus making subjects identifiable, has different effects across regimes, which we explain by different perceptions of responsibility.