In 2017, Amazon reported $5.6 billion of U.S. profits and didn’t pay a dime of federal income taxes on it. The company’s financial statement suggests that various tax credits and tax breaks for executive stock options are responsible for zeroing out the company’s tax this year. The company’s zero percent rate in 2017 reflects a longer term trend. During the previous five years, Amazon reported U.S. profits of $8.2 billion and paid an effective federal income tax rate of just 11.4 percent. This means the company was able to shelter more than two-thirds of its profits from tax during that...