You say same percentage, I say same relative impact to standard of living.
Fair means different things to different people.
How would you determine "relative impact to standard of living"?
Until that's defined, I have to side with "same percentage". Someone show me what's fair about progressive tax rates anyway. You're always left at the whim of some politician to determine what your "fair share" is. Establish what constitutes "taxable" (from among income, investments returns, assorted gains, etc) and apply a flat tax rate. In addition, the combined tax rates of Federal, State and Local should not exceed the share left for the individual.