1. U.S. Census Bureau; Social, Economic & Housing Statistics Division; Washington DC 20233, MD
2. Department of Agricultural Economics; Purdue University; West Lafayette IN 47907
3. Department of Spatial Economics; VU University Amsterdam and Tinbergen Institute; Amsterdam The Netherlands
4. National Institute of Demographic and Economic Analysis; University of Waikato; Hamilton 3240 New Zealand
5. Department of Agricultural Economics; Purdue University; Krannert Building, Room 572, West Lafayette IN 47907