Public Good Experiments with large Groups in a virtual laboratory

公共产品的特点往往是，它们需要由大群体提供，但每个主体为提供公共产品所做的贡献所获得的回报（用mpcr边际替代率来衡量）非常小。在以前的公共产品实验室实验中，不可能调查这种组合（大群体，小MPCR），因为MPCR从下到下受到1/N的限制，并且N的大小（受试者数量）受到几个原因的限制。WE 2027/10-1项目的目标是首次在实验室条件下使用小型mpcr进行大型群体的公共产品实验。这可以通过将四个独立的实验室合并成一个大实验室来实现。到目前为止，这个项目已经让我们成功地进行了8人、60人和100人的实验，mpcr分别为0.25、0.04和0.02。到目前为止，这项工作的结果已被证明是非常有趣的，并部分地在第一份工作文件中提出。我们特别观察到，一个强大的MPCR效应，而群体规模没有显著的影响。一个令人惊讶的结果是，MPCR为0.04的100人的大组与MPCR为0.25的小组（N=8）表现出非常相似的合作水平。然而，直接比较这两种组合是相当困难的，因为组的大小和MPCR参数都是不同的。然而，可以说群体规模和MPCR效应之间一定存在相互作用，但迄今为止尚未得到承认。项目继续进行的目的是通过更多的实验和新的设计来获得对这两种效应相互作用的更多见解。与先前进行的有关购买排放权的实验一样，使用了60名受试者。有一个相对稳定和恒定的平均贡献，20-25%的初始捐赠。然而，贡献遵循的模式与公共物品实验不同。

Public goods are often characterized by the fact that they need to be provided by large groups but that the return each agent receives for their contribution for the provision of the public good (as measured by the MPCR-marginal rate of substitution) is very small. It has not been possible to investigate this combination (large groups, small MPCR) in previous laboratory experiments on public goods because the MPCR is bounded from below by 1/N and the size of N (the number of subjects) is limited for several reasons. The aim of project WE 2027/10-1 is to, for the first time, carry out public goods experiments with large groups with small MPCRs under laboratory conditions. This is made possible by combining four separate laboratories into one large laboratory. Up until now the project has enabled us to successfully carry out experiments with groups of 8, 60, and 100 subjects and MPCRs of 0.25, 0.04 and 0.02. The results of this work have proved to be very interesting thus far and are partially presented in a first working paper. We observed, in particularly, a strong MPCR effect whilst group size has no noteworthy influence. A surprising result was that large groups of 100 subjects with an MPCR of 0.04 showed a very similar level of cooperation to small groups (N=8) with a large MPCR (0.25). A direct comparison of these two combinations is rather difficult, however, since both the group size and the MPCR parameters were varied. However, it is possible to say that there must be an interaction between group size and MPCR effect which has so far not been recognized. The aim of the projects continuation is to win additional insights into the interplay of these two effects through more experiments and a new design. With the experiments previously carried out regarding the purchasing of emissions rights a group of 60 subjects was used. There was a relatively stable and constant average contribution of 20-25% of the initial endowment. However, the contributions follow a different pattern than in the public goods experiments.