Bank Runs: History, Mechanics, and Modern Vulnerabilities
A bank run occurs when a large number of depositors withdraw their money simultaneously because they fear the bank will become insolvent. In March 2023, Silicon Valley Bank collapsed in 48 hours — the fastest bank run in US history — as depositors withdrew $42 billion in a single day.
Bank runs are possible because of the fundamental maturity mismatch in banking: banks take short-term deposits (which can be withdrawn at any time) and make long-term loans (which cannot be called in early). This is called "transforming" short-term liabilities into long-term assets. As long as depositors trust the bank and do not all withdraw at once, the system works. But if enough depositors lose confidence, the bank must sell assets at fire-sale prices to meet withdrawals, which destroys its solvency — creating a self-fulfilling prophecy. The bank fails not because it was genuinely insolvent but because the panic made it insolvent.
The classic model of bank runs was formalized by Diamond and Dybvig (1983), who won the Nobel Prize for their work. They showed that bank runs are an equilibrium — if everyone believes a run will happen, it will happen. The solution, they proved, is deposit insurance. When depositors know their money is safe (up to $250,000 per account in the US), they have no incentive to run. The FDIC was created in 1933 in response to the thousands of bank failures during the Great Depression. From 1934 to 2006, bank failures averaged fewer than 10 per year.
Real-world example: In March 2023, Silicon Valley Bank (SVB) failed after a textbook bank run. SVB had invested a large portion of its deposits in long-term Treasury bonds and MBS. When interest rates rose rapidly in 2022–2023, those bonds lost about $15 billion in market value. Although the losses were unrealized (SVB could hold the bonds to maturity and not realize losses), depositors became nervous. SVB announced a $1.8 billion capital raise on March 8, and a bank run began. By March 9, depositors had withdrawn $42 billion — 25% of total deposits. The FDIC seized the bank on March 10. The run was accelerated by social media and the fact that SVB's depositors were venture capital firms who could move millions with a single text message. The speed was unprecedented — the second-fastest bank run in history (Northern Rock 2007) took weeks, not hours.
Protecting Yourself from Bank Runs
Keep deposits under the FDIC limit of $250,000 per depositor per bank. If you have more than $250,000, spread it across multiple banks or use a CDARS service that distributes deposits among member banks. For large cash holdings, use Treasury bills (backed by the full faith and credit of the US government) or government money market funds (which are highly diversified). Monitor your bank's financial health through its regulatory filings and its ratio of unrealized losses to capital. During the 2023 crisis, banks with high unrealized losses on their bond portfolios and high concentrations of uninsured deposits were the most vulnerable. The key is to ensure your deposits are fully insured — if they are, you have no reason to participate in a run.
FAQs
Is my money safe in a bank run?
If your deposits are under $250,000 per account and your bank is FDIC-insured, your money is fully protected. The FDIC has never failed to make insured depositors whole since 1933. In the SVB failure, all depositors — including those with over $250,000 — were made whole through the systemic risk exception, but this was not guaranteed. Uninsured depositors in other 2023 failures (Signature Bank, First Republic) were also made whole. However, the FDIC is not legally required to protect uninsured deposits. The safest approach is to keep deposits within FDIC limits.
What caused the 2023 regional banking crisis?
The 2023 crisis had three root causes. First, rapid Fed rate hikes (from 0% to 5.25% in 14 months) caused massive unrealized losses on bank bond portfolios — the aggregate loss for US banks was $620 billion. Second, banks had grown their deposit bases rapidly during 2020–2021 and invested those deposits in long-term bonds at low yields. Third, social media and digital banking made it possible for depositors to coordinate runs instantly — a phenomenon called "digital bank runs." The combination of large unrealized losses, high uninsured deposits, and social media velocity created the conditions for fast-moving runs.
Can bank runs happen to money market funds?
Yes — money market funds experienced a "run" in September 2008 when the Reserve Primary Fund "broke the buck" (fell below $1.00 NAV) due to losses on Lehman Brothers commercial paper. Investors rushed to redeem from prime money market funds, causing the government to step in with a temporary guarantee program. In response, the SEC implemented reforms in 2010 and 2016: prime institutional money market funds now have floating NAVs and can impose redemption gates and liquidity fees during stress. Government money market funds (which hold only Treasuries and agency securities) are considered extremely safe and did not experience runs in 2008 or 2020.