First Author:   Ben Halima Mohamed Ali Institute for Research and Information in Health Economics benhalima@irdes.fr   10 rue Vauvenargues Paris, 75008, France   33(0) 1 53 93 43 09(Phone) 33(0) 1 53 93 43 09(Fax) http://www.irdes.fr Second Author: Regaert Camille Institute for Research and Information in Health Economics regaert@irdes.fr   Paris, 75008   33(0) 1 53 93 43 66(Phone) 33 (0) 1 53 93 43 50(Fax) http://www.irdes.fr