Most of those exemptions are relevant, and anyways, the accounting of what constitutes income can be deceiving. I worked in china for 9 years and paid 0% USA taxes because I took a foreign tax credit (I still filled all my income in the 1040). Should that be counted as USA income? Does my 0% drag the average down? Likewise, if that 24% includes foreign income and tax credits, then it is in no way comparable to European numbers that don't include foreign income at all (since no one else taxes global income except a small country in Africa, which isn't a big economy).