This is a very nice chart showing that taxes overall are remarkably close to proportional. One of the things that suggests to me is that a much simpler tax system that had people paying a proportional tax such as a VAT tax, coupled with a lump-sum transfer to the poor, would not be such a big change after all. We probably cause a lot of distortions by pretending to have a progressive tax system instead of admitting that we have a mostly proportional tax system and optimizing it.