1. Department of Agricultural and Resource Economics, University of California, Berkeley, CA 94720, USA
2. Department of Trade and Finance, Faculty of Economics and Management, Czech University of Life Sciences Prague, Kamýcká 129, Prague 6, 165 00 Prague, Czech Republic
3. Institute of Economics and Management, North-Caucasus Federal University, Pushkin Str. 1, 355017 Stavropol, Russia