Rima Lajnaf Faculty of Economics and Management of Sfax   lajnaf.rima@gmail.com sfax, TN 3027 Tunisie   lajnaf.rima@gmail.com             JEL Areas: E5 : Monetary Policy, Central Banking, and the Supply of Money and Credit: General E3 : Prices, Business Fluctuations, and Cycles: General (includes Measurement and Data)