Purchases and sales of government and certain other securities in the open market by the New York Federal Reserve Bank as directed by the FOMC in order to influence the volume of money and credit in the economy. Purchases inject reserves into the depository system and foster expansion in money and credit sales have the opposite effect. Open market operations are the Federal Reserve's most important and most flexible monetary policy tool. They are used to promote either higher or lower growth in money and credit and to offset undesired changes in the reserve positions of depository institutions stemming from movements in currency, float, Treasury deposits, and other factors.