Mario Draghi has opened a door. Janet Yellen has to decide whether she wants to walk through.
The European Central Bank president signaled last week that policy on his side of the Atlantic is going on hold as officials wait to see how their stimulus measures play out. That pause may hand the U.S. Federal Reserve chair an opportunity to raise interest rates in coming months, by reducing the risk of a sharp rally in the dollar if the policies of the two central banks conspicuously diverged.