First Author:   Jesús López-Rodríguez University of A Coruña jelopez@udc.es   Department of Economics,, Harvard University, Littauer Center, 1805 Cambridge Street Cambrdige, 02138, US       Second Author: Antonio García-Lorenzo University of A Coruña aglec@udc.es   Facultad de Ciencias Econóicas, Campus de Elvina s/n A Coruña, 15071, Spain   +34 981167050(Phone) +34981167070(Fax) Third Author: Andrés Faíña University of A Coruna fai@udc.es   Facultad de Ciencias Economicas, Campus de Elvina s/n A Coruña, 15071, Spain   +34 981167050(Phone) +34981167070(Fax)