1. Associate Professor, Department of Agricultural and Applied Economics, 422 Taylor Hall, University of Wisconsin-Madison, Madison, WI 53705, USA.
2. Vice President, Science and Program Strategy, United Soybean Board, 16305 Swingley Ridge Rd. Suite 150, Chesterfield, MO 63017, USA.
3. Research Assistant, University of Bergen, Tennisveien 3D, Oslo 0777, Norway.
4. Professor, System Dynamics Group, Department of Geography, University of Bergen, P.O. Box 7802, 5020 Bergen, Norway