bank run and deposit insurance
A bank takes your deposit and lends most of it out, keeping only a fraction in cash. That works as long as depositors trust the bank and withdraw gradually. But suppose a rumour spreads that the bank is in trouble. Each depositor reasons: if everyone rushes to withdraw, the bank will run out of cash, so I had better get my money out first. Everyone thinking this at once produces a stampede to the doors — a bank run — and the rush itself can sink even a healthy bank, because no fractional-reserve bank can pay all depositors at the same instant.
The cruel logic is that a bank run can be self-fulfilling: the mere fear that a bank might fail makes people withdraw, and the withdrawals are what cause it to fail. It is a coordination problem — if everyone stayed calm, all would be fine; but no individual can afford to stay calm if they fear others won't. Deposit insurance is the main cure. A government agency guarantees that depositors will get their money back up to a set limit (for example, the first $250,000 per account in the United States) even if the bank collapses. Once depositors know their money is safe regardless, they have no reason to join a panic — which means the panic, and the run, usually never starts. The insurance works largely by being believed.
Deposit insurance, together with the central bank acting as a lender of last resort (ready to lend cash to a solvent but illiquid bank in a crisis), is why catastrophic bank-run waves like those of the 1930s became rare. But the safety net has a cost economists openly debate: moral hazard. If depositors are insured, they stop scrutinising whether their bank is prudent, and bankers may take bigger risks knowing the government backstops them. This is why insured banks are also heavily regulated and supervised — the guarantee removes the panic, but it must be paired with rules so that the removed market discipline does not invite reckless banking.
In 2023, depositors at Silicon Valley Bank tried to pull tens of billions of dollars in a single day after fears spread online; the bank, unable to raise that much cash so fast, was seized within hours. Insured depositors were protected up to the limit — a textbook modern bank run, accelerated by smartphones.
A run can topple a bank in hours; deposit insurance removes most depositors' reason to run.
A bank run is usually a liquidity crisis (not enough ready cash) rather than an insolvency one (assets worth less than debts) — though it can turn a solvent bank into a failed one. Deposit insurance stops panics but creates moral hazard, so it must be paired with regulation; the guarantee also typically covers deposits only up to a limit, not every dollar.