First Author:   Sophie Clot LAMETA, UMR 1135, Montpellier Supagro clot@supagro.inra.fr         Second Author: Gilles Grolleau LAMETA, UMR 1135, Montpellier Supagro - LESSAC, Burgundy School of Business grolleau@supagro.inra.fr         Third Author: Lisette Ibanez LAMETA, UMR 1135, INRA ibanez@supagro.inra.fr