Option valuation with conditional skewness

There is extensive empirical evidence that index option prices systematically differ from Black-Scholes prices. Out-of-the-money put prices (and in-the-money call prices) are relatively high compared to the Black-Scholes price. Motivated by these empirical facts, we develop a new discrete time dynamic model of stock returns with Inverse Gaussian innovations. The model allows for conditional skewness as well as conditional heteroskedasticity and a leverage effect. We present an analytic option pricing formula consistent with this stock return dynamic. An extensive empirical test of the model using S&P500 index options shows that the new Inverse Gaussian GARCH model's performance is superior to a standard existing nested model for out-of-the money puts, thus demonstrating the importance of conditional skewness. The discrete-time Inverse Gaussian GARCH process has two interesting continuous-time limits. One limit is the standard stochastic volatility model of Heston (1993). The other is a pure jump process with stochastic intensity. Using these limit results, an equivalent motivation for our model is that it generalizes standard stochastic volatility models by allowing for "jumps"" and other fat-tailed negative movements in stock returns. The empirical results therefore also demonstrate the importance of jumps for the pricing of out-of-the-money puts." Il est clair empiriquement que les prix d'options sur indices diffèrent de manière systématique des prix Black-Scholes. Les prix des options de vente hors du cours (et les prix des options d'achat dans le cours) sont relativement élevés par rapport au prix Black-Scholes. Motivés par ces faits empiriques, nous développons un nouveau modèle dynamique à temps discret de rendements d'actions avec des innovations gaussiennes inverses. Le modèle permet de tenir compte de l'asymétrie conditionnelle ainsi que de l'hétéroskédasticité conditionnelle et d'un effet de levier financier. Nous présentons une formule(This abstract was borrowed from another version of this item.)