This paper contributes in three dimensions to the literature on health care demand. First, it features the first application of a bivariate random effects estimator in a count data setting, to permit the efficient estimation of this type of model with panel data. Second, it provides an innovative test of adverse selection and confirms that high-risk individuals are more likely to acquire supplemental add-on insurance. Third, the estimations yield that in accordance with the theory of moral hazard, we observe a much lower frequency of doctor visits among the self-employed, and among mothers of small children. Copyright © 2002 John Wiley & Sons, Ltd.

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. Terms of use: Documents in Optimal Incentive Contracts under Inequity AversionFlorian Englmaier Achim Wambach The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit company supported by Deutsche Post World Net. The center is associated with the University of Bonn and offers a stimulating research environment through its research networks, research support, and visitors and doctoral programs. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. D I S C U S S I O N P A P E R S E R I E SIZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be available directly from the author. ABSTRACT Optimal Incentive Contracts under Inequity Aversion *We analyze the Moral Hazard problem, assuming that agents are inequity averse. Our results differ from conventional contract theory and are more in line with empirical findings than standard results. We find: First, inequity aversion alters the structure of optimal contracts. Second, there is a strong tendency towards linear sharing rules. Third, it delivers a simple rationale for team based incentives in many environments. Fourth, the Sufficient Statistics Result is violated. Dependent on the environment, optimal contracts may be either overdetermined or incomplete.JEL Classification: D23, D63, J31, J33, M12, Z13

In their seminal work, Rothschild and Stiglitz (1976) have shown that in competitive insurance markets, under asymmetric information, pooling contracts cannot exist in equilibrium, firms make zero profit, and, under some circumstances, equilibrium does not exist. In the present work, the model is extended by introducing unobservable wealth in addition to the differing risks. The study shows that if the differences in wealth are small, different wealth types are pooled while different risks are separated. For large wealth differences, partial risk pooling contracts, in which one type chooses different contracts in equilibrium, are feasible. Furthermore, equilibria with profitmaking contracts can exist. Complete risk pooling contracts can occur only under very restrictive assumptions. The effect of the extra dimension of asymmetric information on the nonexistence problem is ambiguous.

We study non-binding procurement auctions where both price and non-price characteristics of bidders matter for being awarded a contract. The outcome of such auctions critically depends on how information is distributed among bidders during the bidding process. As we show theoretically, whether it is in the buyer's interest to conceal or to disclose non-price information most importantly depends on how important the quality aspects of the good to be procured are to the buyer: The more important the quality aspects are to the buyer, the more interesting concealment becomes. We then empirically study the impact of a change in the information structure using data from a large European online procurement platform for different categories of goods. In a counterfactual analysis we analyze the reduction of non-price information available to the bidders. In the data we find that the choice of information structure indeed matters. Confirming the hypothesis obtained in our theoretical framework, we find that in auction categories where bidders' non-price characteristics are of little importance for the decisions of the buyers, concealment of non-price information decreases buyers' welfare by up to 6% due to reduced competitive pressure leading to higher bids. In contrast, for categories where bidders' non-price characteristics strongly influence buyers' decisions concealment of non-price information increases buyers' welfare by up to 15%. for their helpful comments and suggestions. Sebastian Stoll gratefully acknowledges financial support by the Deutsche Forschungsgemein-schaft (DFG) through GRK 801.