What Is Fractional Reserve Banking? How It Works

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Fractional reserve banking is a system in which banks keep only part of their customers’ deposits as reserves (cash in the vault or balances held at the central bank) and use the rest to make loans and buy other assets. Depositors can still withdraw on demand. The arrangement works because, on an ordinary day, only a small share of depositors asks for its money at once. The same mechanism lets the banking system expand the money supply: a loan creates a new deposit for the borrower, while the original depositor’s balance stays the same.

How Fractional Reserve Banking Works

A deposit is not money the bank stores for you. Legally, it is a loan from you to the bank. The bank records your balance as a liability (it owes you that amount on demand) and holds the funds among its assets. It keeps some of those assets as reserves and puts the rest into loans, securities and other investments that earn more than the bank pays you.

The bank’s profit comes mainly from the gap between what it earns on loans and what it pays on deposits, known as the net interest margin.

Three pieces hold the system together:

1. Reserves. Vault cash plus the balance the bank keeps in its account at the central bank. Banks use these to meet withdrawals, settle payments with other banks and satisfy any reserve requirement.
2. The interbank market. A bank that runs short of reserves can borrow overnight from banks that have extra. In the U.S., these loans happen in the federal funds market.
3. The lender of last resort. If interbank funding is unavailable or too expensive, a bank can borrow from the Federal Reserve’s discount window. The discount rate is set above the federal funds target range, so banks have a reason to seek funds from each other first.

The reserve ratio

The reserve ratio is the share of deposits a bank holds as reserves:

Reserve ratio = Reserves ÷ Deposits

The ratio a regulator requires and the ratio a bank actually holds are two different numbers. A reserve requirement sets a floor, and banks can hold more. Since 2020 U.S. banks have had no required floor at all, yet many still hold large reserve balances, partly because the Federal Reserve pays interest on reserve balances (IORB).

The Money Creation Cycle

When a bank makes a loan, it does not hand over another depositor’s money. It credits the borrower’s account with a new deposit. The borrower spends it, the recipient deposits it at another bank, and that bank can lend out part of it in turn. Each round adds new deposits to the system, while every earlier depositor still holds a full balance.

Example: how one deposit multiplies (hypothetical)

Assume a 10% reserve ratio, that each bank lends out everything above its reserves, and that every loan is spent and redeposited in full at another bank. Start with a $1,000 cash deposit.

The original $1,000 of reserves now supports $10,000 of deposits. Of that total, $9,000 is new money created through lending. The totals follow from the simple money multiplier:

Money multiplier = 1 ÷ reserve ratio Maximum deposits = initial reserves × (1 ÷ reserve ratio)

At 10%, the multiplier is 10. At 20% it would be 5, and at 5% it would be 20. A higher reserve ratio means less expansion.

Example: where the bank’s profit comes from (hypothetical)

Assume a bank pays 1% a year on savings deposits and lends at 5% a year. On $9,000 of loans funded by deposits, it earns $450 a year in interest and pays $90 on the matching deposits, keeping a $360 spread. Defaults, operating costs and the cost of holding reserves all come out of that margin, so the spread is not pure profit.

Why real-world expansion is smaller

The multiplier is a ceiling under idealized assumptions. Actual money creation falls short of it for several reasons:

• People and businesses hold some money as cash instead of redepositing it.
• Banks often keep reserves above the minimum, especially when the central bank pays interest on them.
• Lending depends on creditworthy borrowers who want loans.
• Capital and liquidity rules cap how much a bank can lend relative to its own funding and equity.

Central banks have described the modern process differently from the textbook chain. Loans create deposits first, and banks then obtain the reserves they need in the interbank market or from the central bank. The multiplier is still useful for understanding the direction of the effect, but it does not predict how much money banks will actually create.

Origins and History

The usual origin story of fractional reserve banking involves medieval and early modern goldsmiths. Merchants left gold with goldsmiths for safekeeping and received receipts, which began to circulate as payment because handing over a receipt was easier than moving gold. Goldsmiths noticed that only a small share of the stored gold was reclaimed on a given day, so they lent part of it out at interest and issued receipts exceeding the gold they actually held.

In the United States, formal reserve rules arrived with the national banking system:

• National Bank Act of 1863 and its 1864 revision. These laws chartered national banks and required them to hold reserves against deposits, with requirements of up to 25% for some banks under the system.
• Federal Reserve Act of 1913. This law created the Federal Reserve System, and member banks were required to keep reserve balances with the regional Federal Reserve Banks.
• 1917. Reserve requirements were set at 13%, 10% and 7%, depending on the type of bank.
• 1950s and 1960s. The Fed set required ratios as high as 17.5% for certain banks.
• 2019. Under the tiered structure, banks with less than $16.3 million in net transaction accounts had no reserve requirement. A 3% ratio applied above that level up to $124.2 million, and 10% applied above $124.2 million.
• March 26, 2020. The Federal Reserve reduced the 10% and 3% ratios to 0% for all banks, removing reserve requirements entirely. Interest on reserve balances became the main tool for influencing how much banks keep in reserve.

The legal basis in the U.S. is the Federal Reserve Act, which authorizes the Fed to set reserve requirements, and the Fed’s Regulation D. No law requires banks to hold deposits in full, and banks have never had to do so.

Is Fractional Reserve Banking Still Used?

Yes. A 0% reserve requirement does not end fractional reserve banking. Banks still hold only part of their deposits as reserves and lend or invest the rest. In the U.S., they now hold reserves to meet payments and withdrawals, to satisfy liquidity rules and to earn interest on reserve balances, not to meet a legal minimum.

Lending can still create money under a zero requirement, but the simple multiplier formula stops working. Dividing by a 0% ratio gives no meaningful limit. The constraints that bind instead are:

• Capital requirements. Banks must fund a minimum share of their risk-weighted assets with their own equity. Loan losses reduce capital first, so a bank that lends too aggressively runs out of capital before it runs out of reserves. The capital adequacy ratio measures this buffer.
• Liquidity rules. International standards under Basel III include a liquidity coverage ratio. It requires large banks to hold enough high-quality liquid assets to cover projected outflows during a 30-day stress period.
• Interest rates. The central bank’s policy rate affects what banks pay for funding and what borrowers pay for loans, and so it affects how much borrowing people want to do.

Other central banks still use reserve requirements actively. The People’s Bank of China, for example, raises or lowers its reserve requirement ratio to tighten or loosen lending.

Why It Matters

Fractional reserve banking turns idle deposits into credit. A mortgage works because banks can lend money that depositors are not using right now, and the same is true of auto loans, business credit lines and many other loans.

It also gives policymakers a lever. Raising reserve requirements reduces how much banks can lend and cools activity, while lowering them encourages lending. The Fed rarely used this tool and now relies on interest rates and interest on reserves, but the cost and availability of bank credit still shape spending, hiring and investment.

Fractional Reserve vs. Full Reserve and Gold-Backed Systems

Full reserve (100% reserve) banking requires banks to hold every dollar of demand deposits as reserves. Deposits become pure safekeeping. Banks could not lend them out, so lending would have to come from equity or from investors who knowingly accept the risk, such as buyers of time deposits or loan funds. Supporters argue this would eliminate bank runs on checking accounts. Critics answer that credit would become scarcer and more expensive, and that depositors would likely pay fees instead of earning interest.

A gold standard ties the quantity of currency to a fixed amount of gold. Because the supply of gold grows slowly, the money supply cannot easily keep pace with a growing economy, which tends to push prices down and restrict credit. Historically, many banks under gold standards still operated on fractional reserves of gold. Gold backing and fractional reserves are separate questions.

Limitations and Risks

Bank runs

Most deposits can be withdrawn on demand, but loans cannot be called in overnight. If enough depositors lose confidence at once, a bank runs out of liquid assets even when its loans are sound. Fear of a run can trigger the run.

At the start of the Great Depression, in the banking panics of 1930 to 1931, depositors rushed to withdraw funds. New York’s Bank of the United States collapsed in December 1930. In 2015, during the Greek debt crisis, Greece missed a payment to the International Monetary Fund. As withdrawals mounted, the government closed banks temporarily and imposed capital controls to stop deposits from draining out of the system.

Modern systems reduce run risk in two main ways. Deposit insurance, introduced in the U.S. with the creation of the FDIC in 1933, guarantees insured balances, so small depositors have less reason to rush for the exit. Central banks also lend to solvent banks that face temporary liquidity shortages.

Overheating and inflation

Because lending creates money, rapid credit growth during an expansion can feed demand faster than the economy can produce goods and services. Prices rise, and borrowers take on debt sized for conditions that may not last. When the cycle turns, defaults rise and banks pull back on lending, which can deepen a downturn.

Credit risk and the money multiplier in reverse

Money creation works in both directions. When loans are repaid or written off and banks stop lending, deposits shrink. A wave of bad loans can reduce both bank capital and the money supply at the same time.

Common Confusions

• Reserves vs. capital. Reserves are liquid assets that cover withdrawals and payments. Capital is the bank’s own equity that absorbs losses. A bank can have plenty of reserves and still be insolvent, or be well capitalized and still face a liquidity squeeze.
• A Ponzi scheme. Critics sometimes use this comparison, but the structures differ. A Ponzi scheme pays earlier investors with money from new investors and has no underlying assets. A bank holds loans and securities that generate income, and it is regulated, supervised and backed by deposit insurance and a lender of last resort.

FAQs

The Bottom Line

Anyone with a bank account or a loan depends on this system, which turns idle deposits into mortgages, auto loans and business credit. Reserve requirements in the U.S. fell to 0% in 2020, but banks still hold partial reserves, and capital rules, liquidity rules and interest rates now limit lending. Deposit insurance and central bank lending reduce run risk without removing it.