Questions of differentiation of the population on a level of incomes in Republic Mary El are considered. Parameters of a variation and structure of the basic monetary incomes are analyses. Classification of administrative areas on the parameters describing incomes of the population is lead. The analysis of territorial distinctions of the population on levels of incomes is given. For more in-depth study of interrelation of the parameters describing differentiation of incomes of the population of Republic, on everyone allocated cluster are constructed regression models of a degree of influence of the parameters reflecting age structure of the population on a level of monthly average wages, pensions and social payments.