In a public goods experiment with the opportunity to vote to expel members of a group, we found that contributions rose to nearly 100% of endowments with significantly higher efficiency compared with a noexpulsion baseline. Expulsions were strictly of the lowest contributors, and there was an...

The fact that many people take it upon themselves to impose costly punishment on free riders helps to explain why collective action sometimes succeeds despite the prediction of received theory. But while individually imposed sanctions lead to higher contributions in public goods experiments,...

Recent experiments have shown that voluntary punishment of free riders can increase contributions, mitigating the free-rider problem. But frequently punishers punish high contributors, creating “perverse†incentives which can undermine the benefits of voluntary punishment. In our...