1. Department of Agricultural Economics, Purdue University, West Lafayette, IN 47907-1310, USA; Department of Spatial Economics, Free University, De Boelelaan 1105, 1081 HV Amsterdam, The Netherlands
2. Department of Spatial Economics, Free University, De Boelelaan 1105, 1081 HV Amsterdam, The Netherlands
3. Department of Agricultural Economics, Purdue University, West Lafayette, IN 47907-1310, USA