Alpízar, Francisco, Fredrik Carlsson and Olof Johansson-Stenman. 2008. “Anonymity, Reciprocity and Conformity: Evidence from Voluntary Contributions to a Natural Park in Costa Rica.” EfD Discussion Paper 08.
In a natural field experiment, the authors quantified the importance of anonymity, reciprocity, and conformity through the provision of social reference levels in order to explain voluntary contributions. In the study setting, the effects of the various treatments were small, suggesting that the self-image as an honorable person, irrespective of other people’s opinions, could be an important explanation of contribution behavior. The experiment overall showed no clear evidence that current practice by charitable organizations is inefficient.