Based on the similarity of properties of photons and money, and on the formula for the density of distribution of photon gas by energies, the corresponding mathematical formula for distribution of annual income per capita is obtained. Application of this formula for the data analysis reveals several independent groups of population with different average levels of their income. In particular four main groups of population contribute to the distribution of income in the economy of the USA.
International Frontier Science Letters (Volume 6)
S. G. Fedosin "Group Function of Income Distribution in Society", International Frontier Science Letters, Vol. 6, pp. 6-15, 2015