A bank run (also known as a run on the bank) occurs when a large number of bank customers withdraw their deposits because they believe the bank is, or might become, insolvent. As a bank run progresses, it generates its own momentum, in a kind of self-fulfilling prophecy: as more people withdraw their deposits, the likelihood of default increases, and this encourages further withdrawals. This can destabilize the bank to the point where it faces bankruptcy.
A banking panic or bank panic is a financial crisis that occurs when many banks suffer runs at the same time. A systemic banking crisis is one where all or almost all of the banking capital in a country is wiped out. The resulting chain of bankruptcies can cause a long economic recession. Much of the Great Depression's economic damage was caused directly by bank runs. The cost of cleaning up a systemic banking crisis can be huge, with fiscal costs averaging 13% of GDP and economic output losses averaging 20% of GDP for important crises from 1970 to 2007.
Several techniques can help to prevent bank runs. They include temporary suspension of withdrawals, the organization of central banks that act as a lender of last resort, the protection of deposit insurance systems such as the U.S. Federal Deposit Insurance Corporation, and governmental bank regulation. These techniques do not always work: for example, even with deposit insurance, depositors may still be motivated by beliefs they may lack immediate access to deposits during a bank reorganization.
