The most common measures are named M0 (narrowest), M1, M2, and M3. In the United States they are defined by the Federal Reserve as follows:
- M0: The total of all physical currency, plus accounts at the central bank that can be exchanged for physical currency.
- M1: M0 – those portions of M0 held as reserves or vault cash + the amount in demand accounts (“checking” or “current” accounts).
- M2: M1 + most savings accounts, money market accounts, small denomination time deposits and certificate of deposit accounts (CDs) of under $100,000.
- M3: M2 + all other CDs, deposits of eurodollars and repurchase agreements.
As of March 23, 2006, information regarding M3 will no longer be published by the Federal Reserve, ostensibly because it costs a lot to collect the data but doesn’t provide significantly useful data. The other three money supply measures will continue to be provided in detail. On March 7th, 2006, Congressman Ron Paul introduced H.R. 4892 in an effort to reverse this change.