Financial fragility is the vulnerability of a financial system to a financial crisis. Franklin Allen and Douglas Gale define financial fragility as the degree to which "...small shocks have disproportionately large effects." Roger Lagunoff and Stacey Schreft write, "In macroeconomics, the term "financial fragility" is used...to refer to a financial system's susceptibility to large-scale financial crises caused by small, routine economic shocks." Sources of financial fragility Why does the financial system exhibit fragility in the first place? Why do banks choose to take on a capital structure that makes them vulnerable to financial crises? There are two views of financial fragility which correspond to two views on the origins of financial crises. According to the fundamental equilibrium or business cycle view, financial crises arise from the poor fundamentals of the economy, which make it vulnerable during a time of duress such as a recession. According to the self-fulfilling or sunspot equilibrium view, the economy may always be vulnerable to a financial crisis whose onset may be triggered by some random external event, or simply be the result of herd mentality. Self-fulfilling crisis views Diamond-Dybvig In the standard Diamond-Dybvig model, financial systems are vulnerable to a financial crisis in the form of a bank run due to the inherent nature of banking. Banks serve as intermediaries between depositors and borrowers. Depositors want immediate access to their deposits, while borrowers are not able to pay on demand. This creates a fundamental fragility, as a bank's assets cannot be liquidated in the event of a crisis to pay all depositors. This tension makes the financial system susceptible to a sudden change in demand for money by depositors, resulting in a bank run. Diamond-Rajan Economists Douglas Diamond and Raghuram Rajan argued that banks purposefully adopt a fragile structure as a commitment device. Under this view, depositors would not normally trust banks with their deposits because they fear that when they want to withdraw their money, the bank may try to avoid repaying, or try to repay at a lower rate. However, if the bank does not have enough liquid assets to cover all depositor claims, a refusal to pay any one depositor the promised amount will prompt all other depositors to try to withdraw as well, and effectively cut off all lending to the bank. Banks voluntarily submit themselves to the risk of a bank run so that depositors will trust them with their