How new rules could pinch health stocks

It has been good to be in the health insurance business in recent years. The five largest publicly traded insurers have outperformed the S&P 500 by an average of 15 percentage points so far this year and have solidly outperformed the market since the Affordable Care Act became law in 2010. Investors expect strong second quarter results when UnitedHealth Group reports on Tuesday. At least one provision in the new health bill, governing so-called medical loss ratios, could be a further benefit to insurers. [Registration required.]