Therese Rebière LIRSA-CNAM and IZA   Department of Economics (EFAB) CNAM, case 1D2P30 2 rue Conté Paris, 75003 FRANCE   therese.rebiere@cnam.fr   http://economics.rebiere.free.fr/           JEL Areas: J6 : Mobility, Unemployment, and Vacancies: General J4 : Particular Labor Markets: General