We already have progressive taxation.  We have five brackets and if you include provincial taxes, the top rates range from 47.7% in BC to 54% in Nova Scotia otherwise the rich already have to pay around half their income to the government.  How high does Oxfam think it should be?  We do not have a flat tax and never had so a silly argument.  Now true in some countries like the US they have loopholes that allow the rich to pay a lot less, but the solution is to close the loopholes not raise rates.