Fed Chairman Ben S. Bernanke and Vice Chairman Janet Yellen

Fed Chairman Ben S. Bernanke and Vice Chairman Janet Yellen

Andrew Harrer/Bloomberg

Federal Reserve Chairman Ben S. Bernanke, left, whose second four-year term ends next month, has quadrupled Fed assets since 2008 with bond purchases intended to lower long-term borrowing costs and reduce unemployment. Vice Chairman Janet Yellen, right, who may win Senate confirmation this week to replace Bernanke, has been a supporter of the policy.