First Author:   Ousama Ben-Salha National Engineering School of Gabes and International Finance Group-Tunisia, Tunisia oussama.bensalha@isgs.rnu.tn   Gabes, 6029, Tunisia       http://works.bepress.com/ousama_bensalha/ Second Author: Maamar Sebri Faculty of Economics and Management of Sousse and LaREMFiQ, IHEC, University of Sousse, Tunisia maamer.sebri@isgs.rnu.tn   , Tunisia       http://works.bepress.com/maamar_sebri/