1. Ecares, Université Libre de Bruxelles, Avenue F. D. Roosevelt 50, CP 114, B-1050 Brussels, Belgium and School of Business and Economics, Maastricht University, Tongersestraat 53, 6211 LM Maastricht, The Netherlands(email: )
2. School of Business and Economics, Maastricht University, Tongersestraat 53, 6211 LM Maastricht, The Netherlands(email: )