Social security contributions paid by employees and employers. Unweighted average excluding the Czech Republic, Estonia, Hungary, Poland, the Slovak Republic and Slovenia. Compared with those derived from household surveys, such measures have the main advantage of being unaffected by cross-country differences in the definition of household taxes and by differences in responding to household surveys. The OECD has built synthetic indicators of labour income tax progressivity, based on statutory tax schedules, over a wide income range.18 Focusing on a single wage earner, Figure 12 (Panel A) shows that there is wide cross-country variation in the degree of progressivity of statutory schedules for personal income taxes and employees’ social security contributions.