Skew can be thought of as one side of the distribution being stretched to reflect the greater likelihood of events in either the left or right tail of the distribution. It is a distribution asymmetry. It is the third movement of the distribution and usually is measured as:
However, the measure of skew as a difference cubed does not have immediate intuitive sense. You can measure it as either being positive or negative, and give it a level of intensity, but it does not have a good feel for most users. Investors will like positive skew, but it must be thought of in the context of price. How much do I have to pay for the skew I may like.
Other alternatives to the traditional measure of skew that are easy to calculate for return include:
Low moment skew which is the scaled difference between the sample mean and median.
Spread between the up and down semi-variances which is easy to calculate and has good intuition.
The high minus low measure which is the spread of absolute value of the max and min scaled by the standard deviation.
All can be calculated on a rolling basis to provide insight on the changing skew of any asset.
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