Olivier Musy CRED, University Paris 2 Panthéon Assas   21 Rue Valette PARIS, 75005 France   olivier.musy@u-paris2.fr   https://sites.google.com/site/musyolivier/           JEL Areas: E3 : Prices, Business Fluctuations, and Cycles: General (includes Measurement and Data) E5 : Monetary Policy, Central Banking, and the Supply of Money and Credit: General