Banks typically make loans to customers by crediting new demand deposits to the account of the customer. This practice, which is known as fractional reserve banking, permits the total supply of credit to exceed the liquid legal reserves of the bank. The amount of this excess is expressed as the "reserve ratio" and is limited by government regulators not to exceed a level which they deem adequate to ensure the ability of banks to meet their payment obligations. Under this system, which is currently practiced throughout the world, the money supply varies with the quantity of legal reserves and the amount of credit issuance by banks.