The Zero Bound in U.S. History This figure shows U.S. short-term interest rates, specifically the interest rate on three-month Treasury bills, from 1920 to 2014. As shown by the shaded area at left, for much of the 1930s, interest rates were very close to zero, leaving little room for expansionary monetary policy. After World War II, persistent inflation generally kept interest rates well above zero. However, in late 2008, in the wake of the housing bubble bursting and the financial crisis, the interest rate on three-month Treasury bills was again virtually zero.Sources: National Bureau of Economic Research; Federal Reserve Bank of St. Louis.