Carlo Migliardo University of Messina - Department of Economics (SEAM)   Via dei Verdi,75 MESSINA, 98122 ITALY   cmigliardo@unime.it   http://unime.it/dipartimenti/seam/_dipartimenti?empid=53a09c6ae279254d5223cbae4d24f13f129c1dea           JEL Areas: C1 : Econometric and Statistical Methods: General D4 : Market Structure and Pricing: General