Application of parabolic spline for population income distributions analysis

The aim of the study is an empirical test of the hypothesis about the possibility of using the lognormal function as an adequate model of the distribution of the population by income. The method of spline functions is used as the main research tool. The values of the free parameters of the parabolic spline were determined from the solution of the problem of minimizing the integral smoothness of the distribution function under the condition of its monotonic increase. As the information base of the study, statistical data on the distribution of wages of employees of organizations of the Russian Federation in 2019 were used. This work was supported by the Russian Foundation for Basic Research, grant No. 19-010-000921.