1. Department of Economics, Deakin University, Melbourne, VIC 3125, Australia
2. Center on Food Security and the Environment, Stanford University, Stanford, CA 94305
3. Department of Economics, Stockholm University, Stockholm 106 91, Sweden
4. Global Environmental Policy Unit, Doerr School of Sustainability, Stanford University, Stanford, CA 94305
5. National Bureau of Economic Research, Cambridge, MA 02138