President Barack Obama formally nominated Janet Yellen as the 15th chair of the Federal Reserve on Wednesday, ensuring that the powerful U.S. central bank will be led for the next four years by someone who shares the basic philosophy of the current chairman, Ben Bernanke.

The two agree that the central problem facing the U.S. economy is high unemployment; that the Fed can — indeed is obligated to — use its tools to try to fix that; and that monetary policy, whatever its limitations, is a powerful tool to try to make life better for millions of Americans.

While the philosophy atop the Fed will not be changing, what has changed in the eight years of Bernanke's leadership are the demands of the job.