We develop a model that accounts for the decay of the average contribution observed in experiments on voluntary contributions to a public good. The novel idea is that people's moral motivation is "weak." Their judgment about the right contribution depends on observed contributions by group members and on an intrinsic "moral ideal." We show that the assumption of weakly morally motivated agents leads to the decline of the average contribution over time. The model is compatible with persistence of overcontributions, variability of contributions (across and within individuals), the "restart effect" and the observation that the decay in contributions is slower in longer games. Furthermore, it offers a rationale for conditional cooperation. (This abstract was borrowed from another version of this item.)

Economists recognize that monetary incentives can backfire through the crowding-out of moral and social motivations leading to an overall decrease of the desired behavior. We implement a field experiment where participants are asked to fill a questionnaire on pro-environmental behaviors under different incentive schemes, either with no monetary incentive (control) or with low or high monetary incentive directed either to the respondents or to an environmental cause. We investigate whether (i) there is a significant crowding-out effect, (ii) directing monetary incentive to the cause rather than to the respondents reduces the overall impact of a crowding-out effect, and (iii) offering the choice regarding the money recipient a ects participation. Except for a high monetary incentive where the respondent chooses himself the end-recipient, we show that monetary rewards directed either at the individual or at the cause actually harms intrinsic motivations, but not to the same extent. We formalize our results building on an adaptation of an original model by Bolle and Otto (2010) and introduce agents heterogeneity in terms of intrinsic motivation. This heterogeneity has key implications for the understanding of the crowding-out e ect. Several policy recommendations regarding the use of market-based instruments are drawn. (This abstract was borrowed from another version of this item.)

The need for a global agreement to the problem of tropical deforestation has led to the REDD (Reducing Emissions from Deforestation and Degradation) scheme, which proposes that the developed countries pay developing countries for CO 2 emissions saved through avoided deforestation and forest degradation. The remaining issue is specifying the rules defining payments to countries that reduce their deforestation levels. This article develops a game-theoretic bargaining model, simulating the on-going negotiation process which is currently taking place within the Convention on Climate Change, after the Copenhagen agreement of December 2009. It shows that the conditions under which developing countries are left to bargain over the allocation of the global forest fundmay lead to an ineffective system of incentives. Below a given level of contributions from the North, the mechanism fails to curb deforestation. Beyond this level, it induces perverse effects: the larger the North's contribution, the larger the deforestation decisions. Consequently, the mechanism is most effective only at a specific threshold, which, given the unobservability of countries'preferences, can only be found by a repeated "trial and error" implementation process.

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