Part 1

Marginal rates are fairly straightforward as you pointed out. Reputable organizations have published very different estimates for 'EFFECTIVE' tax rates that corps. Pay. The most recent estimate comes from the World Bank and International Finance Commission, which put the U. S. EFFECTIVE rate for 2014 at 27.9 percent. That’s second-highest behind New Zealand among OECD countries and 15th-highest among the 189 countries measured.

In 2011, the Tax Foundation published a survey of 13 prior estimates of the United States’ effective tax rate from 2005 to 2011. All 13 studies pegged the U.S.’s rate as above average, but none had the U.S. rate first overall.