Marion Podesta LERNA (Toulouse School of Economics & ENAC)   21 allée de brienne Manufacture des tabacs Aile J.J Laffont Toulouse, 31000   marion.podesta@univ-tlse1.fr   http://marionpodesta.wordpress.com/           JEL Areas: D4 : Market Structure and Pricing: General L1 : Market Structure, Firm Strategy, and Market Performance: General