Djimoudjiel Djekonbe University of N'Djamena   Chagoua Ndjamena 6552 NDjamena, Chad 00 Tchad   djimoudjiel_djekonbe@yahoo.fr             JEL Areas: A1 : General Economics: General E2 : Macroeconomics: Consumption, Saving, Production, Employment, and Investment: General (includes Measurement and Data)