Investor base structure as a source of risk is not captured by conventional measures of risk as it relates largely to future to one-off events not previously measured. It is not extrapolated from past volatility. To illustrate this think of another self-fulfilling risk-a bank run. If a large number of depositors were to withdraw their money simultaneously from almost any deposit-talking bank. it would without external assistance face a liquidity crisis. The risk for a depositor is a function of the behaviour of other depositors. The rules a regulator devises to prevent a lack of confidence leading to a bank run are necessarily more art than science. What may seem reasonable and sufficient one day may not the next. After financial crisis reestablishing a bank's credibility, and that of whole banking systems in the developed world, has been uncharted territory.