1. Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey USA
2. Department of Economics Stockholm University Stockholm Sweden
3. Research Institute of Industrial Economics Stockholm Sweden
4. Max Planck Institute for Research on Collective Goods Bonn Germany
5. Jain Family Institute New York USA
6. School of Public and International Affairs Princeton University Princeton New Jersey USA
7. Department of Mathematics and Statistics Vassar College Poughkeepsie New York USA