First Author:   Francesca Lotti Sant'Anna School of Advanced Studies - Pisa, Italy lotti@sssup.it   Laboratory of Economics and Management, Sant'Anna School of Advanced Studies, Via G. Carducci, 40 Pisa, 56127, ITALY   0039 050 883343(Phone) 0039 050 883343(Fax) http://www.sssup.it/~lem Second Author: Enrico Santarelli Economics Department, University of Bologna santarel@spbo.unibo.it   Economics Department, University of Bologna, Strada Maggiore, 45 Bologna, 40125, ITALY   0039 051 2092631(Phone) 0039 051 209(Fax) http://www.dse.unibo.it/~santarel