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Die Dis cus si on Pape rs die nen einer mög lichst schnel len Ver brei tung von neue ren For schungs arbei ten des ZEW. Die Bei trä ge lie gen in allei ni ger Ver ant wor tung der Auto ren und stel len nicht not wen di ger wei se die Mei nung des ZEW dar.Dis cus si on Papers are inten ded to make results of ZEW research prompt ly avai la ble to other eco no mists in order to encou ra ge dis cus si on and sug gesti ons for revi si ons. The aut hors are sole ly respon si ble for the con tents which do not neces sa ri ly repre sent the opi ni on of the ZEW. Das Wichtigste in Kürze Non-technical SummaryThe provision of public goods often faces the problem that agents need to voluntarily decide on their own contributions or -alternatively -have to agree upon some desired provision level of the public good in combination with a specific burden sharing rule. This challenge is particularly demanding, when, in addition to enforcement problems, interests differ among players due to heterogeneous preferences. International climate policy is an important example. While strong free-riding incentives prevent a pure voluntary and uncoordinated solution, international negotiations are loaded with debates on equity issues, i.e. on what constitutes a fair distribution of a global reduction target for greenhouse gas emissions.In this paper, we investigate how burden sharing rules may impact the provision level of a public good that all agents voluntarily accept. We focus on different rule-based contribution mechanisms that are based on the principle of the smallest common denominator: all agents can suggest a minimum provision level of the public good that is allocated across agents according to some predetermined rule. The minimum of all proposals, i.e. the lowest common denominator, then takes effect and creates a "lower bound" for the individual contribution levels. This approach reflects many real world institutional arrangements that either involve a simultaneous choice of provision goal and burden sharing, or sequentially try to first determine the burden sharing rule before then deciding upon the provision goal. Since each participating country needs to sign and ratify the agreement, the player with the smallest proposal is pivotal. Countries can, however, voluntarily go beyond their obligations.We experimentally compare the ability of different rule-based contribution schemes to overcome the inefficiency in public good provision. Players differ with respect to their benefits from the public good, each group consists of two low-type and two high-type agents.Our results indicate that all rule-based contribution schemes significantly increase both payoff levels relative to the standard voluntary contribution mechanism. Interestingly, the equalpayoff rule Pareto-dominates all other rules. This finding is particularly surprising since all rules are predicted to generate coordination on efficient, but differing allocations. Explicitly addressing redistribution among heterogeneous players by equalizing payoffs performs best due ...

Die Dis cus si on Pape rs die nen einer mög lichst schnel len Ver brei tung von neue ren For schungs arbei ten des ZEW. Die Bei trä ge lie gen in allei ni ger Ver ant wor tung der Auto ren und stel len nicht not wen di ger wei se die Mei nung des ZEW dar.Dis cus si on Papers are inten ded to make results of ZEW research prompt ly avai la ble to other eco no mists in order to encou ra ge dis cus si on and sug gesti ons for revi si ons. The aut hors are sole ly respon si ble for the con tents which do not neces sa ri ly repre sent the opi ni on of the ZEW. Abstract:In this paper, we investigate both short-and long-term impacts of financial stimuli on public goods provision when contributions are tied to individual harm-related behavior. We conduct a large-scaled field experiment to examine voluntary contributions to a carbon offsetting program during the online purchase of a bus ticket. We systematically vary the individual payoff structure by introducing different matching grants (1/3:1, 1:1, 3:1) and price rebates (r-25%, r-50%, r-75%). Our results show that price rebates are more effective than matching schemes in raising participation rates while matching grants induce higher contributions to the offsetting program. We suspect differences in the personal responsibility for the compensated emissions to drive this result. Analyzing repeated bookings, we find decreasing treatment effects for returning customers except for the case of 1:1 matching grants. The equal matching scheme is also the only intervention that increases net contributions of customers compared to the control group.

Die Dis cus si on Pape rs die nen einer mög lichst schnel len Ver brei tung von neue ren For schungs arbei ten des ZEW. Die Bei trä ge lie gen in allei ni ger Ver ant wor tung der Auto ren und stel len nicht not wen di ger wei se die Mei nung des ZEW dar.Dis cus si on Papers are inten ded to make results of ZEW research prompt ly avai la ble to other eco no mists in order to encou ra ge dis cus si on and sug gesti ons for revi si ons. The aut hors are sole ly respon si ble for the con tents which do not neces sa ri ly repre sent the opi ni on of the ZEW. Abstract: Voting for Burden Sharing Rules in Public Goods GamesIn this experiment, we endogenize the choice of which contribution scheme is implemented in a public goods game. We investigate three rule-based contribution schemes. In a first step, players agree on a common group provision level using the principle of the smallest common denominator. Subsequently, this group investment is allocated according to a specific rule to individual minimum contributions. The game is implemented either as a Single-or a MultiPhase Game. In the Single-Phase Game, the contribution schemes are exogenously implemented. In the Multi-Phase Game, we let subjects vote on the rule-based contribution schemes. If a scheme obtains a sufficient majority it is implemented. In case no sufficient majority is reached, subjects have to make their contributions to the public good using the voluntary contribution mechanism (VCM). Our results suggest that the endogenous choice of a contribution scheme has an impact on the level of contributions. In case of a rule-based contribution scheme which equalizes payoffs, contributions are higher if subjects choose the scheme than in case the scheme is implemented exogenously. In contrast, contributions are higher if the VCM is implemented exogenously than in case a sufficient majority cannot be obtained and, therefore, subjects have to play the VCM.

We study the effect of a subtle change in the choice architecture on offsetting behavior. In a large-scale field experiment, we examine repeated voluntary contributions to a carbon offsetting program during the online purchase of long-distance bus tickets. In the control group, travelers had the option to offset their carbon emissions resulting from their bus trip, but they could also simply ignore the offer. In the treatment group, travelers were forced to actively choose whether to offset their carbon emissions or not. This "active choice" requirement immediately increased participation in the offsetting program by almost 50%. Investigating returning customers, we find that this treatment remains effective over time. We report evidence that some customers tend to keep avoiding active contribution decisions in subsequent booking decisions.