Gael Giraud Paris School of Economics; CNRS ; ESCP-Europe   75016 Paris 75016 Paris Paris, France   gael.giraud@parisschoolofeconomics.eu   http://ces.univ-paris1.fr/membre/Giraud/pageperso.html           JEL Areas: E5 : Monetary Policy, Central Banking, and the Supply of Money and Credit: General D5 : General Equilibrium and Disequilibrium: General