Yes, value derived per dollar is meaningful, but it is rather difficult to measure reliably. A lot depends on how much corruption there is. However, I'd claim

Yes, value derived per dollar is meaningful, but it is rather difficult to measure reliably. A lot depends on how much corruption there is. However, I'd claim taxes in proportion to GDP are a fairly good indicator of taxes in proportion to income, because income and GDP are strongly related. In fact, one way to define GDP is "the sum of primary incomes distributed by resident producer units" and the same number may be called GDI, "gross domestic income".