1. Department of Marketing, Business Economics and Law, and Department of Economics, University of Alberta, Edmonton, Alberta, Canada T6G 2R6.
2. IDEI and LERNA, University of Toulouse I (Sciences Sociales), 21 allée de Brienne, 31000 Toulouse, France.
3. INRA-LAMETA, 2 Place Viala 34060–Montpellier cedex 1, France.