To best understand how President Trump's plan to cut the corporate tax rate from 35% to 20% would affect companies, it's necessary to determine a company's effective tax rate. WalletHub is on the case. The outlet reviewed annual reports for the top 100 companies on the S&P index to determine federal, state, and international tax rates in 2016. The overall tax rate, on average, is about 27%, roughly what it was in 2015. Here are the companies with the highest and lowest effective tax rates—which Forbes previously noted is not necessarily what they pay: