English: The visualisation, from Piketty and Saez (2007) shows estimated average tax rates in France, the US and the UK, at two points in time: 1970 and 2005. Notice that these are average rates (i.e. total tax contributions as a share of pre-tax income), which are different to marginal tax rates.

Displayed are rates for the bottom 90% of the income distribution, as well as higher percentiles. Again, we can see in these estimates that the systems in question are progressive – increasingly higher percentiles in the income distribution pay increasingly higher effective rates of taxation. However, the lines are much flatter in 2005, which shows that the systems have become less progressive at the top: the average share of income paid by those at the very top of the income distribution has dropped substantially since 1970. This is important because, as the authors of the figure point out, over the same period pre-tax income inequality grew significantly: a few very rich individuals at the very top are accumulating an increasingly large share of national incomes.

An important point that should be kept in mind is that these estimates are not directly comparable to those from the Congressional Budget Office discussed above, because they do not take into account government transfers, and rely on different methodological assumptions – for example, they do not consider excise taxes (but they do consider estate taxes). For more details see Piketty and Saez (2007).