In the work on the basis of real information the concentration and differentiation of monetary income by population groups of the Russian Federation are investigated. It is proposed to use not only formal quantile, but also so-called "income" groups to characterize the distribution of population, and to characterize the ratio of "income" groups of population - the stratification coefficient. For the first time in the study of monetary incomes of the population, the gerfindal concentration coefficient was used in the analysis.