Pierre O. de Souza Management School, Federal University of Rio Grande do Sul, Porto Alegre, Brazil   Doutor Plínio Barreto Street 173, 23A – Bela Vista São Paulo, SP 01313020 Brazil   pierresouza_@hotmail.com             JEL Areas: G1 : General Financial Markets: General (includes Measurement and Data) C6 : Mathematical Methods and Programming: General