1. Department of Psychology and Woodrow Wilson School of Public Affairs, Princeton University, Princeton, NJ, USA.
2. National Bureau of Economic Research, Cambridge, MA, USA.
3. Busara Center for Behavioral Economics, Nairobi, Kenya.
4. Center for Global Development, Washington, DC, USA.
5. Max Planck Institute for Collective Goods, Bonn, Germany.
6. Department of Ecology and Evolutionary Biology and Woodrow Wilson School of Public Affairs, Princeton University, Princeton, NJ, USA.