Franck Martin University of Rennes 1 and Crem   Franck Martin 7, Place Hoche 35065 Rennes Cedex Rennes, Bretagne 35065 France   franck.martin@univ-rennes1.fr   http://perso.univ-rennes1.fr/franck.martin/           JEL Areas: C4 : Econometric and Statistical Methods: Special Topics G1 : General Financial Markets: General (includes Measurement and Data)