First Author:   Chiara Monfardini Dipartimento di Scienze Economiche, Università di Bologna chiara.monfardini@unibo.it   Piazza Scaravilli 2 Bologna, Italia       http://www2.dse.unibo.it/dsa/profile.php?id=56 Second Author: Joao Santos Silva Department of Economics, University of Essex jmcss@essex.ac.uk   Wivenhoe Park Colchester, CO4 3SQ, United Kingdom   +44 (0) 1206872769(Phone)   http://www.essex.ac.uk/economics/people/staff/jmcss.shtm