For example, money may have been destroyed, or stored as a form of security (the proverbial “money under the mattress”), or by coin collectors, or held in reserve within the banking system, including currency held by foreign central banks as a foreign exchange reserve asset.
The monetary authority of each country (or currency zone) is responsible for ensuring there is enough money in circulation to meet the commercial needs of the economy, and releases additional notes and coins when there is a demand for them.
Cash that is in the hands of individuals and businesses in the community may be needed for routine or exceptional purchases or held in reserve.
In 1990, total currency in circulation in the world passed the equivalent of one trillion United States dollars.
The Bank for International Settlements provides detailed statistics of the worth of banknotes and coins for 18 major currencies used by the member states of the Committee on Payments and Market Infrastructures (CPMI).