First Author:   Mauricio Bugarin University of Brasilia bugarin@unb.br   Department of Economics, ICC Norte, Asa Norte Brasilia, 70910-900, Brazil   55-61-2723548(Phone) 55-61-2723548(Fax) http://www.unb.br/ih/eco/mesp/professores/bugarin Second Author: Mauricio Bugarin University of Brasilia bugarin@unb.br