A 5% increase in income taxes would raise my income taxes from $10.00 tax per $100.00 earned to $10.50 tax per $100.00 earned, moving me from the 10% tax bracket into the 10.5% tax bracket, which is not too bad. If they move me from the 10% tax bracket to the 15% tax bracket that will increase my taxes by 50%, which is awful.
Well, since there was no such thing as a 10.5% tax bracket before the Bush tax cuts, allowing the Bush tax cuts to expire will not change the tax bracket from 10% to 10.5% but rather from 10% to 15%. The lowest tax brackets will have the largest increase (50%) in their taxes on a percentage basis.