Abstract
Our meta-analysis investigates the impact of Leading-by-Example on voluntary contributions towards a public good. In such experiments, an appointed leader contributes ahead of the other members. The fellow group members observe the contrition of the leader, before contributing themselves. Using 273 groups as independent observations, we compare the results of Leading-by-Example with a simultaneous contribution structure. Moreover, we focus on the impact of Leading-by-Example on the followers. Our results indicate that the establishment of a leader indeed leads to increasing contributions compared to leaderless groups. The effect does not decrease in long-term. Followers’ contributions are positively correlated with the example set by the leader. However, followers employ an imperfect matching strategy. Therefore, we can confirm the ‘leader’s curse’. Last, not least, we find a positive effect of group size on leadership.

Keywords
Leading-by-Example, Cooperation, Meta-analysis, Voluntary contribution

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Abstract
We test a parsimonious theory on how group formation changes competitive behavior. Our experimental treatments systematically modify prize sharing rules to explain behavioral differences in contests of individuals and inter-group contests. The results show that group formation itself does not lead to a change in competitive behavior at the aggregate level. However, our results confirm our predictions that prize sharing foster contest expenditure because meritocratic prize sharing reduces the risk among the contestants. We also observe that egalitarian prize-sharing – a standard feature in inter-group contests – reduces expenditure. Further analysis indicates no significant evidence for a general outgroup hostility. Instead, we observe a conditional in-group preference as expenditures increases with the contributions of fellow group members.

Keywords
Contests, Groups, Ingroup/outgroup bias

Abstract
We investigate the relationship between intragroup cooperation and attrition rates in an online experiment with an innovative design. We let participants earn money with a tedious work task. We encourage attrition with decreasing net payments over time. We compare the results from this simple setting with behavior in two treatments in which participants can either keep their earnings or contribute them to a common pool. One of the additional treatments also allows for leading-by-example. We observe that successful cooperation delays attrition. Moreover, groups with low initial contribution rates also suffer from rather premature attrition. Peer effects explain this behavior to some extent, but we do not find evidence for a direct causal impact of failed cooperation on attrition.

Keywords
Attrition, Online-Experiment, Task Motivation, Voluntary Contribution, Cooperation

Abstract
We study how growing teams affects leadership effectiveness and intra-group cooperation. We place people in groups of six and subdivided them in two teams of three players. In each team, the members voluntarily contribute to a club good. At the end of a round they receive information about the contributions in their own team and in the other team. In one of the two teams, the members observe the contribution of a randomly chosen leader before they decide themselves. Two treatments allow for migration between the teams. In one of these two treatments participants control access to their team with a voting process. By design, participants can achieve the efficient outcome only if they all move into one team. We compare the results with two treatments which vary team size exogenously. The results show a virtuous circle between leadership, team size and contributions. Leaders foster contributions which encourages migration into their teams. In turn, larger teams experience even more courageous leadership and higher contributions. Nevertheless, the dismissal of potential newcomers in the treatment with voting suggests that team members see a trade-off between team size and contributions. They sacrifice economic benefits from potential entrants in order to maintain intra-team cooperation.

Keywords
Public Goods Game, Group Change, Cooperation, Group Size, Leading-by-example