In this paper we contrast the Concentration Hypothesis developed by Bergmann (1971 and 1974) for the 1986-1997 period. This “hypothesis” maintain that women concentration in a few occupations caused by discrimination, produce a decrease in wages of all individuals in these occupations. Also, we make the Macpherson and Hirsch (1995) decomposition of wages differences to obtain the share of discrimination and no-discrimination components in the wage difference obtained. The results show that female concentration affects all individuals in one occupation, but women are the most affected since female wages decreased more than male wages in the “female” occupations. The wage differential decomposition shows that gender difference was decreased in the period. However, is the non discriminatory component which contributes to a less difference, whereas the discriminatory component increases during the period. In special, the feminization is the part of the wage differential that rises.