Rodolphe Dos santos ferreira BETA, University of Strasbourg   2 rue des Veaux 2 rue des Veaux Strasbourg, 67000 France   rdsf@unistra.fr   http://www.beta-umr7522.fr/-DOS-SANTOS-FERREIRA-Rodolphe           JEL Areas: D4 : Market Structure and Pricing: General E3 : Prices, Business Fluctuations, and Cycles: General (includes Measurement and Data)