M1: One measure of the money supply that includes all coins, currency held by the public, traveler's checks, checking account balances, NOW accounts, automatic transfer service accounts, and balances in credit unions. M2 : One measure of the money supply that includes M1, plus savings and small time deposits, overnight repos at commercial banks, and non-institutional money market accounts. A key economic indicator used to forecast inflation. M3 : One measure of the money supply that includes M2, plus large time deposits, repos of maturity greater than one day at commercial banks, and institutional money market accounts.