The chatter about the Federal Reserve shrinking its massive $4.5 trillion balance sheet and its huge $1.7 trillion portfolio of agency MBS has continued in recent days, with one Fed official talking up the idea and another describing how the U.S. central bank plans to do it. Federal Reserve Bank of St. Louis President James Bullard said in a speech last week that the Fed could begin normalizing its balance sheet. “The Fed’s balance sheet has been an important monetary policy tool during the period of near-zero policy rates,” Bullard said. Thus far, the Fed’s Open Market Committee has not set...