[en]This paper is an empirical study that aims at explaining economic fluctuations and behavior mark-up. Inspired by the method of Roeger (1995), we perform a study of four OECD countries (Denmark, Finland, Italy and the United States) for 17 manufacturing industries covering the period 1986-2008. This study provides a comparison between our estimates of mark-up and other observations on mark-up pricing (Oliveira, Scarpetta and Pilat (1996), Roger (1995) and Rotemberg and Woodford (1992)). It also provides an interpretation of the estimated markups that depend on the type of market structure. An application of a VAR model is used to examine the relationship between imperfect competition and the effects fiscal policy on output and mark-up, based on the method of Rotemberg and Woodford (1999).[/en]