The Federal Reserve's carefully scripted decision to raise interest rates last December, and begin a return to "normal" policy, may now become a nightmare for the U.S. central bank if an economic downturn forces a return to unconventional methods. Fed chair Janet Yellen told lawmakers this week she was studying ways to "be prepared" in the event the current slide in world stock markets, concern about financial sector stress, and slowing economic growth all translate into a recession or another financial crisis. But Yellen said the policy tool of negative interest rates, now favored by some foreign central banks offers ... (full story)