Janet Yellen, vice chair of the Board of Governors of the U.S. Federal Reserve System, is shown prior to addressing the University of California Berkeley Haas School of Business in Berkeley, California in this file photo from November 13, 2012. Former Treasury Secretary Lawrence Summers' withdrawal from consideration to succeed Federal Reserve Chairman Ben Bernanke turns the focus on Janet Yellen. REUTERS/Robert Galbraith/Files (UNITED STATES - Tags: BUSINESS POLITICS EDUCATION)