1. Agricultural Economics and Policy Group, ETH Zurich, 8092 Zürich, Switzerland;
2. Department of Agricultural, Food, and Resource Economics, Michigan State University, East Lansing, Michigan 48824, USA;
3. Research Division on Competitiveness and System Evaluation, Agroscope, 8356 Ettenhausen, Switzerland;
4. Crop Science Group, ETH Zurich, 8092 Zürich, Switzerland;