Most previous studies on intertemporal labor supply found very small or insignificant substitution effects. It is possible that these results are due to constraints on workers' labor supply choices. We conducted a field experiment in a setting in which workers were free to choose hours worked and effort per hour. We document a large positive elasticity of overall labor supply and an even larger elasticity of hours, which implies that the elasticity of effort per hour is negative. We examine two candidate models to explain these findings: a modified neoclassical model with preference spillovers across periods, and a model with reference dependent, loss-averse preferences. With the help of a further experiment, we can show that only loss-averse individuals exhibit a negative effort response to the wage increase.

Casual evidence as well as daily experience suggest that many people have a strong aversion against being the 'sucker' in social dilemma situations. As a consequence, those who cooperate may be willing to punish free-riding, even if this is costly for them and even if they cannot expect future benefits from their punishment activities. A main purpose of this paper is to show experimentally that there is indeed a widespread willingness of the cooperators to punish the free-riders. Our results indicate that this holds true even if punishment is costly and does not provide any material benefits for the punisher. In addition, we provide evidence that free-riders are punished the more heavily the more they deviate from the cooperation levels of the cooperators. Potential free-riders, therefore, can avoid or at least reduce punishment by increasing their cooperation levels. This, in turn, suggests that in the presence of punishment opportunities there will be less free riding. Testing this conjecture is the other major aim of our paper.

In a wide variety of settings, spiteful preferences would constitute an obstacle to cooperation, trade, and thus economic development. This paper shows that spiteful preferences - the desire to reduce another's material payoff for the mere purpose of increasing one's relative payoff - are surprisingly widespread in experiments conducted in one of the least developed regions in India (Uttar Pradesh). In a one-shot trust game, the authors find that a large majority of subjects punish cooperative behavior although such punishment clearly increases inequality and decreases the payoffs of both subjects. In experiments to study coordination and to measure social preferences, the findings reveal empirical patterns suggesting that the willingness to reduce another's material payoff - either for the sake of achieving more equality or for the sake of being ahead - is stronger among individuals belonging to high castes than among those belonging to low castes. Because extreme social hierarchies are typically accompanied by a culture that stresses status-seeking, it is plausible that the observed social preference patterns are at least partly shaped by this culture. Thus, an exciting question for future research is the extent to which different institutions and cultures produce preferences that are conducive or detrimental to economic development.

Most previous studies on intertemporal labor supply found very small or insignificant substitution effects. It is not clear, however, whether these results are due to institutional constraints on workers’ labor supply choices or whether the behavioral assumptions of the standard life cycle model with time separable preferences are empirically invalid. We conducted a randomized field experiment in a setting in which workers were free to choose their working times and their efforts during working time. We document a large positive wage elasticity of overall labor supply and an even larger wage elasticity of labor hours, which implies that the wage elasticity of effort per hour is negative. While the standard life cycle model cannot explain the negative effort elasticity, we show that a modified neoclassical model with preference spillovers across periods and a model with reference dependent, loss averse preferences are consistent with the evidence. With the help of a further experiment we can show that only loss averse individuals exhibit a significantly negative effort response to the wage increase and that the degree of loss aversion predicts the size of the negative effort response.

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The data in Fehr and Tyran (2001) and Petersen and Winn (2014) show that money illusion plays an important role in nominal price adjustment after a fully anticipated negative monetary shock. Money illusion affects subjects' expectations, and causes pronounced nominal inertia after a negative shock but much less inertia after a positive shock. Thus Petersen and Winn (2014) provide a misleading interpretation of both our and their own data.

Interaction in small groups is often affected by concerns for fairness and reciprocity. These effects have to be taken into account in the design of optimal incentive schemes. In Fehr and Schmidt (2004) and Fehr, Alexander Klein and Schmidt (2007, henceforce FKS) we have shown experimentally that “bonus contracts ” that rely on fairness and trust as an enforcement device can be more efficient and more profitable than “incentive contracts ” that are enforced by the courts. In the current paper we consider contracts that combine a voluntary bonus with enforceable incentive payments. The question is whether the combination of these two instruments improves efficiency or whether the use of explicit incentives undermines the functioning of implicit incentives such as voluntary bonus payments. Voluntary bonus payments are frequently used in situations where the principal and the agent both observe some aspects of the agent’s performance, but where it is impossible to contract explicitly on this information because it is not verifiable to the courts. In a one-shot relationship a purely self-interested principal would never pay the bonus and thus the agent would have no incentive to work. However, our previous experiments (FKS 2007, Fehr and Schmidt 2004) show that many principals make substantial voluntary bonus payments, even if the interaction with the