Wall Street stocks are getting crushed

It's been a strong year for the U.S. economy, but not for Wall Street stocks.

Bottom line: The nation's biggest banks have lost value in 2018, despite generally strong earnings, increased corporate merger activity, rising interest rates and all of them passing their first round of Federal Reserve "stress tests." There is no firm consensus on why it's happening, although higher U.S. Treasury yields are a popular culprit.