1. DIAG; Sapienza University of Rome; Rome 00185 Italy
2. CNRS-LEM (UMR 9221); IÉSEG School of Management; 3 rue de la Digue Lille F-59000 France
3. Department of Production Engineering; Universidade Federal de Pernambuco; Recife PE 50670-901 Brazil
4. Economics Department; Rice University; Houston TX 77005-1892 USA