Monday, September 20, 2010


Another look at the nature of risk in the coverage of EMH in the FT.

Second is the pro-cyclical nature of value-at-risk, a measure of the risk of loss. Recent high market volatility is sharpening attention towards risk and the need to measure and manage it. At the same time, rapid financial innovation has increased the ability to monitor and control risks, allowing measures like Var to gain further ground. This would all be good news, if the markets were using the right type of Var for establishing the risk limits.

Generally, when prices move down, Var goes up, eventually triggering the risk limits and thus enlarging the troops of sellers. Symmetrically, the reduction of Var in good times encourages traders and fund managers to pile on risk, increasing their risk exposures when prices are already high and while demand is thriving. This can compound the positive feedback mentioned earlier.

The interesting thing here is the way that a period of low volatility will provide a sample of low volatility and increased risk taking. Increased volatility leads to less risk taking. Can we model this?

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