Lamia Soltani fezzani Univ. Manouba, ESCT, QUARG UR17ES26, Campus Universitaire Manouba, 2010, Tunisia   Residence Malika,Appt I-3-4 Manouba, Manouba 2010 Tunisie   soltanilam@gmail.com             JEL Areas: C1 : Econometric and Statistical Methods: General Q : Agricultural and Natural Resource Economics