I have a great source for you for progressive tax rates from Jewish history. See Making of a Godol p. 28 where he writes that some Jewish communities put a tax on meat of about 5%. They felt that if someone was wealthy enough to purchase meat, then there responsibility towards the poor was great enough that the community would tax them. Just don't turn this into a post on how Torah values support the dems. You know full well that it is silly to say that Torah values support any political party!