The implied volatility term structure of stock index options

This paper tests the expectations hypothesis of the term structure of implied volatility for several national stock market indexes. The tests indicate that the slope of at-the-money implied volatility over different maturities has predictive ability for future short-dated implied volatility, although not to the extent predicted by the expectations hypothesis. The low forecast power may be due to failure to control for a risk premium in the prices of the options. Evidence is presented that a time-varying risk premium proportional to the level of market volatility is consistent with the results.