First Author:   Cheikh Tidiane Ndiaye LARES : University Gaston Berger cheikh-tidiane.ndiaye@ugb.edu.sn   BP234, UFR SEG, UGB Saint-Louis, Senegal   +221 33 961 18 19(Phone) +221 33 961 18 19(Fax) Second Author: Samuel Bates LEDa: PSL Research University (Paris-Dauphine) samuel.bates@dauphine.fr   Place du Maréchal de Lattre de Tassigny Paris Cedex 16, 75775, France   +33 1 44 05 49 47(Phone)