Opluštilová, M. How the measurement of tax progressivity is determined by input data. Diploma thesis. Brno: Mendel University, 2018. The diploma thesis deals with the influence of input data on the final values of the measurement of tax progressivity. For the calculation of the Gini coefficient and other selected indicators for 2015 are used data from Household Budget Survey and the Statistics on Income and Living Conditions (EU-SILC), which are published by the Czech Statistical Office. It was also examined the impact of equivalence scales on the Gini coefficient before taxation and after taxation, as well as the impact of the change in the quantile distribution of income from deciles to quintiles, which occurred in 2016 in Household Budget Survey. The results of the thesis show the significant impact of the chosen survey and the quantile distribution of income. On the other hand, it shows the negligible impact of equivalence scales.