Due to the frequent use of upper contribution limits and the flat payment schedule below those limits, they are slightly regressive on average (but particularly so in Poland). With contribution burdens approximately proportional to incomes, even sizable changes in the overall contribution burden change the redistributive effect by a relatively small amount (top graph of Panel B). Overall rate structures have essentially remained the same over the period. Where progressivity did change (Finland, Poland), contributions rates are low, so that the redistributive effect of these changes is negligible.