Fractional-reserve banking

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Fractional-reserve banking is the banking practice in which banks keep only a fraction of their deposits in reserve (as cash and other highly liquid assets) and lend out the remainder, while maintaining the simultaneous obligation to redeem all these deposits upon demand. Fractional reserve banking necessarily occurs when banks lend out any fraction of the funds received from deposit accounts. This practice is universal in modern banking.

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Prior to the 1800s, savers looking to keep their valuables in safekeeping depositories deposited gold coins and silver coins at goldsmiths, receiving in turn a note for their deposit (see Bank of Amsterdam). Once these notes became a trusted medium of exchange an early form of paper money was born, in the form of the goldsmiths' notes.^[3]
As the notes were used directly in trade, the goldsmiths observed that people would not usually redeem all their notes at the same time, and they saw the opportunity to invest their coin reserves in interest-bearing loans and bills. This generated income for the goldsmiths but left them with more notes on issue than reserves with which to pay them. A process was started that altered the role of the goldsmiths from passive guardians of bullion, charging fees for safe storage, to interest-paying and interest-earning banks. Thus fractional-reserve banking was born.
However, if creditors (note holders of gold originally deposited) lost faith in the ability of a bank to redeem (pay) their notes, many would try to redeem their notes at the same time. If in response a bank could not raise enough funds by calling in loans or selling bills, it either went into insolvency or defaulted on its notes. Such a situation is called a bank run and caused the demise of many early banks.^[3]
Repeated bank failures and financial crises lead to the creation of central banks – government institutions that oversee and regulate commercial banks, impose reserve requirements, and act as lender-of-last-resort if a bank is low on liquidity. The emergence of central banks mitigated the dangers associated with fractional reserve banking.