Julio Ruiz Claeyssen Federal University of Rio Grande do Sul (UFRGS)   UFRGS - Instituto de Matemática Av. Bento Gonçalves, 9500 - Agronomia Sala B111 Porto Alegre, RS 91509-900 Brazil   jcrclaeyssen@yahoo.com   http://www.mat.ufrgs.br/~julio           JEL Areas: R1 : General Regional Economics (includes Regional Data) O1 : Economic Development: General