A bank run occurs when many customers withdraw deposits from a bank within a short period because they fear losing access to their funds or suffering losses. These withdrawals can exhaust the institution’s readily available liquidity, forcing it to seek emergency funding, sell assets, or close. A run may reflect genuine financial weakness, but expectations of other depositors’ withdrawals can also make fears self-fulfilling. When distress spreads across institutions, individual runs can develop into a banking panic. (nobelprize.org)
Why banks are vulnerable
Banks perform financial intermediation by connecting savers with borrowers. They commonly finance longer-term loans and investments with deposits that customers can withdraw on demand or at short notice. This maturity transformation provides depositors with convenient access to funds while supporting investments that take time to generate returns. Its vulnerability is that assets and liabilities have different repayment schedules: a bank cannot necessarily recover its loans immediately when depositors demand payment. (nobelprize.org)
A bank’s balance sheet therefore requires a distinction between liquidity and solvency. Liquidity concerns the ability to meet payments when due; solvency concerns whether assets are sufficient to cover liabilities. A solvent institution may be unable to satisfy unusually large immediate withdrawals without selling assets at depressed prices. Conversely, obtaining short-term funding does not necessarily repair underlying losses. Bank capital absorbs losses, whereas liquid assets provide resources for payments; the two protections serve different purposes. (nobelprize.org)
Expectations and withdrawal incentives
The Diamond–Dybvig model, published in 1983, explains how deposit arrangements can provide valuable liquidity insurance while also allowing a run equilibrium. When depositors expect the bank to continue operating, those without immediate spending needs can leave their funds deposited. If they instead expect widespread withdrawals and premature liquidation, withdrawing early may become individually advantageous. The bank’s outcome consequently depends partly on what depositors believe others will do. (nobelprize.org)
This is a coordination problem within game theory, not simply an example of irrational crowd behavior. Depositors can have understandable incentives to withdraw even when their collective action damages the institution. Information asymmetry compounds the problem because customers may have difficulty assessing the quality of bank assets. Rumors, announcements of losses, or the failure of another institution can therefore influence decisions alongside evidence about the bank itself. Actual runs may combine deteriorating fundamentals with self-reinforcing expectations. (nobelprize.org)
Insurance coverage also affects incentives. Depositors whose balances are not fully protected face possible losses if a bank fails, giving them stronger reasons to move funds quickly. Concentration matters as well: a relatively small number of large, closely connected customers can withdraw substantial amounts almost simultaneously. (fdic.gov)
Transmission and economic effects
A run can force a bank to undertake fire sales—rapid asset disposals at unfavorable prices. Resulting losses can weaken its capital position, transforming a funding problem into a solvency problem. Distress can spread through financial contagion when customers reassess other banks or when falling asset prices affect institutions holding similar investments. Historically, banking panics have extended well beyond the institution where withdrawals first intensified. (nobelprize.org)
Bank failures can also damage the wider economy by disrupting lending relationships and the information banks accumulate about borrowers. Replacing those relationships is costly, and reduced credit availability can hinder business activity. Research on the Great Depression emphasizes that banking disruption was not merely a symptom of economic contraction: it helped deepen and prolong it. (nobelprize.org)
Run-like dynamics are not confined to ordinary deposits. Shadow banking institutions that finance longer-term assets with short-term obligations can face comparable pressure when creditors refuse to renew funding. Such withdrawals of funding were important during the 2007–2009 financial crisis, even where no queues formed outside bank branches. (nobelprize.org)
Institutional safeguards
Deposit insurance reduces the incentive to withdraw by protecting eligible balances if a bank fails. Its effectiveness depends on the coverage provided and confidence in the protection. However, insurance can create moral hazard by weakening incentives for depositors to monitor banks and potentially encouraging greater risk-taking. Insurance arrangements are therefore considered alongside supervision, capital requirements, and other safeguards. (fdic.gov)
A central bank can act as a lender of last resort, providing liquidity when private funding becomes unavailable. Such support may involve lending against eligible collateral under specified conditions. It addresses payment pressures but is distinct from measures intended to absorb losses or resolve a failed institution. (bankofengland.co.uk)
The Basel accords include liquidity standards designed to strengthen resilience. The Liquidity Coverage Ratio requires an adequate stock of unencumbered high-quality liquid assets for a specified 30-day stress scenario. The Net Stable Funding Ratio addresses funding stability over a longer horizon. These standards concern preparedness for stress rather than a guarantee that every possible run can be met. (bis.org)
Historical and digital-era examples
In the United States, banking panics in 1930 and early 1931 were initially regional but became nationwide from autumn 1931. Depositor withdrawals and demands to exchange dollar assets for gold placed simultaneous pressures on the banking system. Federal deposit insurance began operating in 1934 following the establishment of the Federal Deposit Insurance Corporation in 1933. (federalreservehistory.org)
The failure of Silicon Valley Bank in March 2023 illustrates the speed of modern runs. The Federal Reserve reported that the bank lost more than $40 billion in deposits on March 9. Its concentrated, largely uninsured depositor base, networked customers, social-media communication, and digital banking technology contributed to exceptionally rapid withdrawals. The episode combined underlying interest-rate and liquidity vulnerabilities with an abrupt collapse in depositor confidence. (federalreserve.gov)