Expectations Hypothesis of the Term Structure of Implied Volatility: Evidence from Foreign Currency and Stock Index Options

Using a stochastic volatility option pricing model, we show that the implied volatilities of at-the-money options are not necessarily unbiased and that the fixed interval time-series can produce misleading results. Our results do not support the expectations hypothesis: long-term volatilities rise relative to short-term volatilities, but the increases are not matched as predicted by the expectations hypothesis. In addition, an increase in the current long-term volatility relative to the current short-term volatility is followed by a subsequent decline. The results are similar for both foreign currency and the S&P 500 stock index options. , .