What Happens During a Bank Run?
A bank run occurs when many depositors simultaneously try to withdraw their money from a bank out of fear it is insolvent — triggering a self-fulfilling crisis, since no bank can meet the simultaneous withdrawal demands of all depositors.
How It Works
Bank runs exploit the fundamental vulnerability of fractional reserve banking: banks hold only a fraction of deposits as liquid cash. In normal times, only a small percentage of depositors want their money simultaneously, and the bank's daily cash inflows cover daily cash outflows with ease. But if confidence breaks — due to rumors, news of losses, or visible signs of stress — depositors rush to withdraw before others do, fearing they will be last in line if the bank fails.
The self-fulfilling nature of bank runs is their most dangerous characteristic. Even a perfectly solvent bank can be destroyed by a run, because its assets are mostly loans — long-term, illiquid instruments that cannot be quickly converted to cash. To meet withdrawal demands, the bank must sell assets at distressed prices, further impairing its balance sheet and triggering more withdrawals.
The US has experienced three major eras of bank runs. The Great Depression (1929-1933) saw roughly 9,000 US banks fail, devastating the economy and wiping out uninsured depositors. The creation of FDIC insurance in 1933 largely eliminated retail bank runs for 75 years by guaranteeing deposits up to a set limit. The 2007-2008 financial crisis saw a modern bank run — on wholesale funding rather than retail deposits — at Bear Stearns, Lehman Brothers, and money market funds.
The 2023 banking crisis introduced the concept of the digital bank run. When concerns emerged about Silicon Valley Bank's unrealized losses in March 2023, depositors with the SVB app could initiate wire transfers from their phones without going to a branch. Over $40 billion in deposits left SVB in a single day — the fastest bank run in history. SVB failed within 36 hours of the run beginning.
Why It Matters
Bank runs are the reason the entire regulatory framework of modern banking exists. FDIC insurance, Federal Reserve lending facilities, capital requirements, and stress tests all exist primarily to prevent bank runs or contain them when they occur. Understanding bank runs helps explain why depositors are given special protection in bankruptcy — the systemic risk of bank failures spreading through the economy justifies extraordinary government backstops.
For digital finance, the 2023 SVB crisis raised an important question: has digital banking made bank runs faster and more dangerous? The answer appears to be yes — smartphone-enabled instant transfers allow a bank run to complete in hours rather than days, leaving regulators with very little time to respond. This dynamic may push regulators toward more aggressive early intervention when bank stress appears.
Real-World Example
Silicon Valley Bank (SVB) was the 16th largest US bank in February 2023. In March, it disclosed a $1.8 billion loss from selling securities at depressed values and announced plans to raise capital. Tech venture capitalists — major SVB depositors — warned their portfolio companies to move deposits immediately. On March 9, depositors tried to withdraw $42 billion in a single day — more than 25% of SVB's entire deposit base. SVB could not meet the demands, was taken over by regulators on March 10, and was the second-largest bank failure in US history.
Frequently Asked Questions
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Keep Reading
What Is Fractional Reserve Banking?
Fractional reserve banking is the system by which commercial banks hold only a fraction of customer deposits as liquid reserves while lending out the majority — simultaneously creating the money supply and generating profit.
How Banks Use Deposits
When you deposit money in a bank, the bank does not keep it in a vault — it immediately puts your money to work by lending most of it to other customers at much higher interest rates, keeping only a small fraction in reserve.
Why Banks Care About Deposits
Deposits are the single most important input to a bank's business model — they are the cheapest source of funding available, and without them, banks cannot make loans, earn profits, or fulfill their role in the economy.