Fractional reserve banking

Fractional-reserve banking is the practice whereby a bank accepts deposits, makes loans or investments, and holds reserves equal to a fraction of its deposit liabilities. Reserves are held as currency in the bank, or as balances in the bank's accounts at the central bank. Fractional-reserve banking is the current form of banking practiced in most countries worldwide.

Fractional-reserve banking allows banks to act as financial intermediaries between borrowers and savers, and to provide longer-term loans to borrowers while providing immediate liquidity to depositors (providing the function of maturity transformation). However, a bank can experience a bank run if depositors wish to withdraw more funds than the reserves held by the bank. To mitigate the risks of bank runs and systemic crises (when problems are extreme and widespread), governments of most countries regulate and oversee commercial banks, provide deposit insurance and act as lender of last resort to commercial banks.

Because banks hold reserves in amounts that are less than the amounts of their deposit liabilities, and because the deposit liabilities are considered money in their own right, fractional-reserve banking permits the money supply to grow beyond the amount of the underlying base money originally created by the central bank. In most countries, the central bank (or other monetary authority) regulates bank credit creation, imposing reserve requirements and capital adequacy ratios. This can limit the amount of money creation that occurs in the commercial banking system, and helps to ensure that banks are solvent and have enough funds to meet demand for withdrawals. However, rather than directly controlling the money supply, central banks usually pursue an interest rate target to adjust the rate of inflation and bank issuance of credit.

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