On the discrepancy between the objective and risk neutral densities in the pricing of European options

Abstract

A technique known as calibration is often used when a given option pricing model is fitted to observed financial data. This entails choosing the parameters of the model so as to minimise some discrepancy measure between the observed option prices and the prices calculated under the model in question. This procedure does not take the historical values of the underlying asset into account. In this paper, the density function of the log-returns obtained using the calibration procedure is compared to a density estimate of the observed historical log-returns. Three models within the class of geometric Lévy process models are fitted to observed data; the Black-Scholes model as well as the geometric normal inverse Gaussian and Meixner process models. The numerical results obtained show a surprisingly large discrepancy between the resulting densities when using the latter two models. An adaptation of the calibration methodology is also proposed based on both option price data and the observed historical log-returns of the underlying asset. The implementation of this methodology limits the discrepancy between the densities in question.

On the calibration of stochastic volatility models to estimate the real-world measure used in option pricing

“…This is a common problem that plagues illiquid option markets like South Africa. Another challenge is that the estimated density resulting from the calibration to option prices can differ substantially from the estimated density of the historical log returns (see, Visagie and Grobler [19]).…”