UnitedHealth Group’s stock rose about 4% early Tuesday morning, offering a slight hint of relief in an otherwise brutal year, with the company’s third-quarter earnings suggesting the worst of the turmoil may have passed, at least for now. But those earnings are also a powerful reminder that the U.S.’s healthcare math, whether corporate or federal, just does not add up. They also arrive as the federal government remains shut down over a Republican-led refusal to fund an extension of the Affordable Care Act ...