Regressive tax is terrible for a society, I think we can agree. Sasha just asked for an example of regressive tax, and this is what popped in my mind. Jungle law leads to brutal and savage outcomes, not something any sane person would desire. Personally, I believe best tax structure is probably a progressive land tax as that would put the burden on the backs of Ted Turner and Bill Gates (largest US land holders), and stop large scale real estate speculation.