LAUSR

The paper deals with two related topics - a mathematical model of the Gini coefficient, and its application in the taxation theory. However, the mathematical part of the paper should not only be understood as a traditional methodological starting point, but it has also didactic character and correctly describes the properties of the Gini coefficient, pointing to misinterpretation deficiencies found in a number of contemporary works. In the application part of the paper, we study the fulfillment of redistribution function of the tax system in the Czech Republic by using the Musgrave-Thin index coefficient M. Our research implies that the global progressivity of the tax allowance system in the Czech Republic was moderately progressive throughout the analyzed period 2006-2016. The considerable change in the personal income tax structure made in 2008 did not essentially reflect the global tax progressivity. Key words: tax progressivity, Gini coefficient, Lorenz curve, redistribution