President Trump proposed a one-year 10% cap on credit card interest rates by Jan. 20, spooking investors and driving American Express shares down about 4% on Monday. American Express reported third-quarter revenue up 11% to a record $18.4 billion and earnings per share up 19% to $4.14, with net interest income rising 12% to $4.5 billion and card member spending growth accelerating to 9%.