Volatility of the short rate in the rational lognormal model

A recent article of Flesaker and Hughston introduces a one factor interest rate model called the rational lognormal model. This model has a lot to recommend it including guaranteed finite positive interest rates and analytic tractability. Consequently, it has received a lot of attention among practioners and academics alike. However, it turns out to have the undesirable feature of predicting that the asymptotic value of the short rate volatility is zero. This theoretical result is proved rigorously in this article. The outcome of an empirical study complementing the theoretical result is discussed at the end of the article. European call options are valued with the rational lognormal model and a comparably calibrated mean reverting Gaussian model. unsurprisingly, rational lognormal option values are considerably lower than the analogous mean reverting Gaussian option values. In other words, the volatility in the rational lognormal model declines so quickly that options are severely undervalued.     

An Empirical Analysis of the Pricing of Bank Issued Options versus Options Exchange Options

Since 1998, large investment banks have become active as issuers of options, generally referred to as call warrants or bank‐issued options. This has led to an interesting situation in the Netherlands, where simultaneously call warrants are traded on the stock exchange, and long‐term call options are traded on the options exchange. Both entitle their holders to buy shares of common stock. We start with a direct comparison between call warrants and call options, written on the same stock and with the same exercise price, but where the call option has a longer time to maturity. In 13 out of 16 cases we find that the call warrants are priced higher, which is a clear violation of basic option pricing rules. In the second part of the analysis we use option pricing models to compare the pricing of call warrants and call options. If implied standard deviations from options are used to price the call warrants, we find that the call warrants are strongly overpriced during the first five trading days. The average overpricing is between 25 and 30%. Only a small part of the overpricing can be explained by rational arguments such as transaction costs. We suggest that the overvaluation can be explained by a combination of an active financial marketing by the banks and the framing effect.     

On the qualitative effect of volatility and duration on prices of Asian options

We show that under the Black–Scholes assumption the price of an arithmetic average Asian call option with fixed strike increases with the level of volatility. This statement is not trivial to prove and for other models in general wrong. In fact we demonstrate that in a simple binomial model no such relationship holds. Under the Black–Scholes assumption however, we give a proof based on the maximum principle for parabolic partial differential equations. Furthermore we show that an increase in the length of duration over which the average is sampled also increases the price of an arithmetic average Asian call option, if the discounting effect is taken out. To show this, we use the result on volatility and the fact that a reparametrization in time corresponds to a change in volatility in the Black–Scholes model. Both results are extremely important for the risk management and risk assessment of portfolios that include Asian options.     

Analytic approximation formulae for European crack spread options

In this paper, we investigate and compare the pricing of European crack spread call options under different underlying models. New proposed univariate and explicit constant elasticity of variance (CEV) models are assumed and new analytic approximation formulae in the form of asymptotic expansions are derived. As well we derive an analytic approximation formula based on an explicit version of two correlated Schwartz models. In order to compare the performance of our new formulae with the performance of current popular formulae, we calibrate market prices of short tenor heating oil crack spread call options (traded on the New York Mercantile Exchange) and empirically test their performances. Results from the analysis show that our univariate-based CEV formulae outperforms known univariate formulae in capturing market prices. Overall, however we found the explicit approach to be superior to the univariate approach and in particular our new explicit-based formulae performed best in capturing market prices for options with short tenor.     

Are embedded calls valuable? Evidence from agency bonds

This paper examines the call option values embedded in callable agency bonds. For FHLB, FNMA, and SLMA bonds, call value estimates range from 1.23% of par to 1.47% on average, which are between those for the treasury and corporate debt securities. FHLMC bonds, on the other hand, have an average call value estimate of 2.85%. Call values are significantly larger for bonds with a longer remaining maturity and greater default risk. Most interestingly, call values in the call protection period are significantly larger than those in the callable period except for the SLMA bonds, whereas previous studies on corporate debt find no significant difference in call values between these two periods.