It is very easy to understand the arithmetic of this. If someone is earning, say, $120,000 per annum and they have a family to pay, other than either their rent or their interest payments, everything they spend will be incurring GST at the rate of 15 percent, which is, effectively, a tax on their income. For people who are on higher incomes, they save more of their earnings and they don't pay GST on their savings, and no one's suggesting they should. But the effect of that is that the effective tax paid by higher-income people, when you take into account both income tax and GST, is generally lower than is already being paid by middle-income people.