Investors still trust flawed model despite credit crisis lessons?
If market movements followed a normal distribution, such a plunge would be extremely surprising. But what's really astonishing is that investors still appear to be relying on risk management techniques that were rubbished by the credit crisis, said Peter Thal Larsen.
The central flaw lies in believing that price movements in financial products follow a normal distribution around a central mean. Small fluctuations are common. Larger jumps or falls -- the narrow "tails" of a distribution charted on a graph -- are more rare. So anyone using this analysis to look at the oil market would have been very surprised by last week's selloff.
Clive Capital, the commodities hedge fund, has written to investors to point out that the drop in the Brent crude oil contract was a five standard deviation event, according to the Financial Times.
In a normal distribution, such an event should happen on just one trading day in every 1.7 million -- or about once every 7,000 years. But this type of analysis has been comprehensively undermined by the credit crisis.
To begin with, extreme movements happen much more regularly than they should if normal distribution data held true. Moreover, these fluctuations do not happen randomly, but tend to be clustered together. In other words, the "tails" are longer and fatter than the theory suggests.
Indeed, a glance at historical price movements shows the flaws of assuming oil price movements are normally distributed. The Brent crude price has moved, as it did last week, by 9.5 per cent or more on 33 days in the past two decades.
Copyright 2008 www.tradearabia.com
Copyright 2011 Al Hilal Publishing & Marketing Group
Provided by Syndigate.info an Albawaba.com company