1 Department of Economics and School of Global Environmental Sustainability, Colorado State University, Fort Collins, CO 80253-1771, USA. edward.barbier@colostate.edu.
2 Department of Economics and School of Global Environmental Sustainability, Colorado State University, Fort Collins, CO 80253-1771, USA.
3 College of Business and School of Global Environmental Sustainability, Colorado State University, Fort Collins, CO 80253-1201, USA.