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FRM Part II · FRM Exam Part II · Volatility Smiles and Volatility Surfaces

In a stochastic volatility model for an equity option, the correlation between the asset price shocks and the volatility shocks is set to a strongly negative value. Compared with zero correlation, what is the main effect on the implied volatility smile?

A strongly negative price-volatility correlation produces a downward-sloping skew with higher implied volatility at low strikes. Volatility rises as prices fall, creating a fat left tail and thin right tail, whereas zero correlation would give a roughly symmetric smile.

  1. AA symmetric smile with higher curvature at both wings
  2. BA downward-sloping skew with higher implied volatility for low strikesCorrect
  3. CAn upward-sloping skew with higher implied volatility for high strikes
  4. DA flat smile with a higher overall level only

Explanation

Negative correlation means volatility rises when the price falls, fattening the left tail and thinning the right tail of the risk-neutral distribution. This lifts implied volatility for low strikes, giving a downward skew. Zero correlation instead gives a symmetric smile driven by the volatility of volatility.

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