Kuznets had success to solve numerous problems ranging from lack of sources of information and bias assessments, to the development of the theoretical concept of national income. Kuznets achieved a high precision in calculations. His works allowed us to analyze the structure of the national income, and expose to detailed study a number of specific problems of the national economy. Improved methods for calculating the national income and related indicators have become classics and formed the basis of the modern system of national accounts. Having analyzed the distribution of income among different social groups, Kuznets put forward the hypothesis that in countries, which were on the early stages of economic development, income inequality increased first, but as far as national economy was growing, it tended to decrease. This assumption formed the basis of so-called "Kuznets curve" empirical conception.