This study reports evidence from a field experiment that was conducted to investigate the relevance of gift exchange in a natural setting. In collaboration with a charitable organization, we sent roughly 10,000 solicitation letters to potential donors. One-third of the letters contained no gift, one-third contained a small gift, and one-third contained a large gift. Treatment assignment was random. The results confirm the economic importance of gift exchange. Compared to the no gift condition, the relative frequency of donations increased by 17 percent if a small gift was included and by 75 percent for a large gift. The study extends the current body of research on gift exchange, which is almost exclusively confined to laboratory studies.

We study subjects who were asked to fill letters into envelopes with a remuneration independent of output. In the "pair" treatment, two subjects worked at the same time in the same room, and peer effects were possible. In the "single" treatment, subjects worked alone, and peer effects were ruled out. We find evidence of peer effects in the pair treatment because the standard deviations of output are smaller within pairs than between pairs. Moreover, average output is higher in the pair treatment: thus, peer effects raise productivity. Finally, low-productivity workers are the most sensitive to the behavior of peers.

This paper studies the impact of incentives on worker self-selection in a controlled laboratory experiment. Subjects face the choice between a fixed and a variable payment scheme. Depending on the treatment, the variable payment is a piece rate, a tournament, or a revenue-sharing scheme. We find that output is higher in the variable-payment schemes compared to the fixed-payment scheme. This difference is largely driven by productivity sorting. In addition, different incentive schemes systematically attract individuals with different attitudes, such as willingness to take risks and relative self-assessment as well as gender, which underlines the importance of multidimensional sorting.

We analyze the consequences of control on motivation in an experimental principal-agent game, where the principal can control the agent by implementing a minimum performance requirement before the agent chooses a productive activity. Our results show that control entails hidden costs since most agents reduce their performance as a response to the principal's controlling decision. Overall, the effect of control on the principal's payoff is nonmonotonic. When asked for their emotional perception of control, most agents who react negatively say that they perceive the controlling decision as a signal of distrust and a limitation of their choice autonomy.

Do employers and workers underbid prevailing wages if there si unemployment? Do employers take advantage of workers' underbidding by lowering wages? Do employers take advantage of workers underbidding by lowering wages? We hypothesize that under conditions of incomplete labor contracts, wage levels may positively affect workers' propensity to cooperate. This, in turn, may prevent firms from underbidding or accepting the underbidding of workers. Experimental double auctions conducted for the purpose of examinating these hypotheses yield the following results: (i) Workers' underbidding is very frequent, but employers refuse to accept workers' low wage offers in markets with complete labor contracts, employes accept and actively enforce wages close to the competitive level. (ii) Workers' effort is positively related to the wage level. Therefore over their effort level. This holds true even in the presence of explicit performance incentives.

Promotions play an important role for the provision of incentives in firms. We analyze incentives in multistage elimination tournaments with controlled laboratory experiments. In our two main treatments, we compare a two-stage tournament to a one-stage tournament. Subjects in the two-stage treatment provide excess effort in the first stage, both with respect to Nash predictions and compared to the strategically equivalent one-stage tournament. Additional control treatments confirm that excess effort in early stages is a robust finding and suggest that above-equilibrium effort might be driven by limited degrees of forward-looking behavior and subjects deriving nonmonetary value from competing.

In a laboratory experiment we show that minimum wages have significant and lasting effects on subjects' reservation wages.The temporary introduction of a minimum wage leads to a rise in subjects' reservation wages which persists even after the minimum wage has been removed.Firms are therefore forced to pay higher wages after the removal of the minimum wage than before its introduction.As a consequence, the employment effects of removing the minimum wage are significantly smaller than are the effects of its introduction.The impact of minimum wages on reservation wages may also explain the anomalously low utilization of subminimum wages if employers are given the opportunity of paying less than a minimum wage previously introduced.It may further explain why employers often increase workers' wages after an increase in the minimum wage by an amount exceeding that necessary for compliance with the higher minimum.At a more general level, our results suggest that economic policy may affect people's behavior by shaping the perception of what is a fair transaction and by creating entitlement effects.

This paper investigates the driving forces behind informal sanctions in cooperation games and the extent to which theories of fairness and reciprocity capture these forces. We find that cooperators' punishment is almost exclusively targeted toward the defectors, but the latter also impose a considerable amount of spiteful punishment on the cooperators. However, spiteful punishment vanishes if the punishers can no longer affect the payoff differences between themselves and the punished individual, whereas the cooperators even increase the resources devoted to punishment in this case. Our data also discriminate between different fairness principles. Fairness theories that are based on the assumption that players compare their own payoff to the group's average or the group's total payoff cannot explain the fact that cooperators target their punishment at the defectors. Fairness theories that assume that players aim to minimize payoff inequalities cannot explain the fact that cooperators punish defectors even if payoff inequalities cannot be reduced. Therefore, retaliation, i.e., the desire to harm those who committed unfair acts, seems to be the most important motive behind fairness-driven informal sanctions. Copyright The Econometric Society 2005.

We provide evidence that long-term relationships between trading parties emerge endogenously in the absence of third party enforcement of contracts and are associated with a fundamental change in the nature of market interactions. Without third party enforcement, the vast majority of trades are initiated with private offers and the parties share the gains from trade equally. Low effort or bad quality is penalized by the termination of the relationship, wielding a powerful effect on contract enforcement. Successful long-term relations exhibit generous rent sharing and high effort (quality) from the very beginning of the relationship. In the absence of third-party enforcement, markets resemble a collection of bilateral trading islands rather than a competitive market. If contracts are third party enforceable, rent sharing and long-term relations are absent and the vast majority of trades are initiated with public offers. Most trades take place in one-shot transactions and the contracting parties are indifferent with regard to the identity of their trading partner. Copyright The Econometric Society 2004.