Houssem Eddine CHEBBI Faculty of Economic Sciences and Management of Nabeul (FSEGN)   Merazga - Route Hammamet Nabeul, 8000 Tunisia   houssemeddine.chebbi@isaas.rnu.tn   http://chebbi.chez.com/           JEL Areas: C5 : Econometric Modeling: General Q : Agricultural and Natural Resource Economics