M1 money is a country's basic money supply that's used as a medium of exchange. M1 includes demand deposits and checking accounts, which are the most used exchange mediums through the use of debit cards and ATMs. Of all the components of the money supply, M1 is defined the most narrowly. Money supply data is recorded and published, usually by the government or the central bank of the country. Public and private sector analysts monitor changes in the money supply because of the belief that such changes affect the price levels of securities, inflation, the exchange rates, and the business cycle.