[1] Univ Lille 1, Dept Econ, EQUIPPE, Bat SH2,Bur 32, F-59655 Villeneuve Dascq, France
[2] Univ Evry, EPEE, Evry, France
[3] CNRS, 106-112 Bd Hop, F-75647 Paris 13, France
[4] Univ Paris 01, Paris Sch econ, Ctr Econ Sorbonne, 106-112 Bd Hop, F-75647 Paris 13, France