The Federal Reserve System changed its approach to implementing monetary policy on October 6, 1979. Prior to that date, it attempted to reduce fluctuations in short-run interest rates as a means of achieving, along with interest rate stability, a degree of control over movements in the monetary aggregates. On October 6, however, the Federal Reserve shifted its focus from movements in short-run interest rates to movements in reserves held by the banking system. Shortly thereafter, in early 1980, the Federal Reserve announced major redefinitions of the monetary aggregates.