1. U.S. Department of Agriculture; Economic Research Service; Room 7-187B, 1400 Independence Ave., S.W., Mail Stop 1800 Washington, DC 20250-0002 USA
2. Division of Resource Management; West Virginia University; 2044 Agricultural Sciences Building; 101 Research Way Morgantown WV 26505 USA
3. Department of Agricultural and Consumer Economics; University of Illinois at Urbana-Champaign, 344 Mumford Hall; Urbana IL 61801 USA
4. Escuela de Econom´ıa; Administraci´on y Turismo, Universidad Nacional de R´ıo Negro; Villegas 147 San Carlos de Bariloche 8400 R´ıo Negro Argentina
5. Inter-American Foundation, Representative for Belize; Guatemala, and Panama; 1331 Pennsylvania Ave, NW, 12th Floor North, Suite 1200 Washington, DC 20004 USA