Massimiliano Piacenza University of Torino, Dept. of Economics and Public Finance "G. Prato"   University of Torino - School of Economics Dept. of Economics and Public Finance "G. Prato" Corso Unione Sovietica 218 bis Torino, 10134 Italy   piacenza@econ.unito.it   http://web.econ.unito.it/piacenza