First Author:   Miloudi Kobiyh CREM, university of Caen miloudi.kobiyh@unicaen.fr   , UFR sciences écnomiques , 19 rue Claude BLOCH Caen, 14000, France   00 33 2 31 56 55 27(Phone) 00 33 2 31 56 55 27(Fax) Second Author: Ahmed Doghmi CREM university of Caen ahmed.doghmi@unicaen.fr   UFR sciences écnomiques , UFR sciences écnomiques , 19 rue Claude BLOCH Caen, 14000, France   00 33 2 31 56 55 27(Phone) 00 33 2 31 56 55 62(Fax)