Giulio Bottazzi Scuola Superiore Sant'Anna   P.zza Martiri della Liberta', 33 Pisa, 56127 Italy   bottazzi@sssup.it   http://www.sssup.it/~bottazzi           JEL Areas: L2 : Firm Objectives, Organization, and Behavior: General D4 : Market Structure and Pricing: General