First Author:   Sergio Da Silva Department of Economics, Federal University of Rio Grande Do Sul, and National Council for Scientific and Technological Development, Brazil email@sergiodasilva.com   Department of Economics, Federal University of Rio Grande Do Sul, Av Joao Pessoa 52 Porto Alegre, 90040-000, Brazil   + 55 51 3316 4164(Phone) + 55 51 3316 4164(Fax) Second Author: Guilherme Moura Department of Economics, Federal University of Rio Grande Do Sul guilherme@ppge.ufrgs.br         Third Author: Sidney Caetano Department of Economics, Federal University of Rio Grande Do Sul, and Federation of Trade Associations of Rio Grande Do Sul sidneymc@ppge.ufrgs.br