U.S. Federal Reserve Chair Janet Yellen arrives for a news conference in Washington D.C., capital of the United States, on Sept. 20, 2017. The U.S. Federal Reserve on Wednesday kept interest rate unchanged, but announced that it will start to unwind its 4.5-trillion-U.S. dollar balance sheet from October, a further step to end the loose monetary policy. (Xinhua/Yin Bogu)