First Author:   JULIAN RAMAJO UNIVERSITY OF EXTREMADURA ramajo@unex.es   Department of Economics, Faculty of Economics and Business, Elvas Avenue s/n Badajoz, 06071, Spain   0034-924-289-547(Phone) 0034-924-289-547(Fax) http://eco.unex.es/jramajo/jrh_eng.htm Second Author: JAVIER SALINAS UNIVERSITY OF EXTREMADURA / INSTITUTE FOR FISCAL STUDIES javier.salinas@ief.minhac.es   Department of Economics, Faculty of Economics and Business, Elvas Avenue s/n Badajoz, 06071, Spain     0034-924-272-509(Fax) Third Author: FRANCISCO PEDRAJA UNIVERSITY OF EXTREMADURA pedraja@unex.es   Department of Economics, Faculty of Economics and Business, Elvas Avenue s/n Badajoz, 06071, Spain     0034-924-272-509(Fax) Fourth Author: MIGUEL MÁRQUEZ UNIVERSITY OF EXTREMADURA mmarquez@unex.es   Department of Economics, Faculty of Economics and Business, Elvas Avenue s/n Badajoz, 06071, Spain     0034-924-272-509(Fax)