We investigate the effect of a donation incentive tied to contributions to a public good when group members can decide on the size of the donation to be made. An up to 20 % donation of the public good was implemented either exogenously or endogenously by group members. In the Vote treatment,...

Explicit and implicit incentives and opportunities for mutually beneficial voluntary cooperation co-exist in many contractual relationships. In a series of eight laboratory gift-exchange experiments, we show that incentive contracts can lead to crowding out of voluntary cooperation even after...