Ivan M. Castelar Federal University of Ceará (UFC)   Rua Dep. Moreira da Rocha, 577/1000 Fortaleza, Ceará 60160-060 Brazil   ivan@caen.ufc.br   https://caen.ufc.br/pt/           JEL Areas: C1 : Econometric and Statistical Methods: General C4 : Econometric and Statistical Methods: Special Topics