Federal Reserve Chair Janet Yellen said on Thursday she was open to raising a threshold for determining a bank’s systemic importance and indicated that U.S. lenders had made progress in their submissions of so-called living will plans this month. The tacit nod of approval from the Fed chief is a good sign for Wall Street, as a rejection can be costly, though Yellen also made clear the U.S. central bank will not hesitate to reject certain plans when it completes its assessment.