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Similarly to volatility smile, volatility skew indicates the shape of the curve traced by the implied volatility of a security with respect to the strike price. However, instead of the typical U shape of the smile, volatility skew is determined by implied volatility values – these are higher for out-of-the-money strikes than for at-the-money strikes, while at-the-money implied volatility values are higher than those for in-the-money strikes. This pattern results in a decreasing curve. Skew for put options mirrors that of call options. Volatility skew is observed more often in equity markets and is attributable to the large positions of pension funds, insurance companies and asset management firms in out-of-the-money puts, used to insure portfolios against market drawdowns.
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