The Federal Reserve has announced new rules banning top officials from owning individual stocks and bonds, and restricting their trading activities. The move comes after a controversy over whether central bank officials should be able to trade while their policies can move markets. Officials will be restricted to owning mutual funds, which they must hold for at least a year, and will need permission to buy or sell. The new rules aim to assure the public that Fed officials maintain a single-minded focus on the public mission of the Federal Reserve.