This paper develops a model for valuing options on a currency which is maintained within a band. The starting point of our model is the well known Krugman model for exchange-rate behavior within a target zone. Results from model runs provide insight into evidence reported by other authors of mispricing of currency options by extensions of the Black-Scholes model.

This paper extends the Krugman target zone model by including a realignment mechanism. Various properties of that realignment mechanism are discussed. The movement of the exchange rate is governed both by a Wiener process on fundamental and by a Poisson jump process with endogenous realignment size. The realignment mechanism is such that (except in cases where a speculative attack occurs) no jump in fundamental is needed to accompany the jump in the exchange rate. A risk neutral valuation of currency options is constructed. Some properties of option values under realignment risk are illustrated by numerical results.

This volume is a collection of classical and recent empirical studies of currency options and their implications for issues of exchange rate economics, such as exchange rate risk premium, volatility, market expectations, and credibility of exchange rate regimes. It contains applications on how to extract useful information from option market data for financial forecasting policy purposes. The subjects are discussed in a self-contained, user-friendly format, with introductory chapters on currency option theory and currency option markets. The book can be used as supplementary reading for graduate finance and international economics courses, as training material for central bank and regulatory authorities, or as a reference book for financial analysts.

This paper analyzes whether and how central banks can use currency options to lower exchange rate volatility and maintain (implicit) target zones in foreign exchange markets. It argues that selling rather than buying options will result in market makers dynamically hedging their long option exposure in a stabilizing manner, consistent with the first objective. Selling a “strangle” allows a central bank to increase the credibility of its commitment to a target zone, and could have a lower expected cost than spot market interventions. However, this strategy also exposes the central bank to an unlimited loss potential.

A new way of modeling the dynamics of an exchange rate target zone is presented. In the presence of a single upper (resp. lower) target boundary, the exchange rate is precisely represented as the sum of a free float and a short (resp. long) position in a call (resp. put) option with strike price at the boundary. To model a target zone (with two boundaries), a natural approach consists in describing the exchange rate dynamics as the combination of the two, namely the sum of free float together with a long position in a put written on the lower boundary and a short position in a call option written on the upper boundary, respectively. We show that this first order approximation leads to significant mispricing (as much as 20%) and must be iterated, leading to an infinite sequence of compounded 'mirrored' option prices. We analyze basic properties of such mirrored nested options analytically, describe how to calculate them numerically, and show why it is crucial to take into account higher order corrections in realistic target zones. We argue that this analogy to option prices allows for conceptually simple generalizations that describe different target zone arrangements. We apply our methodology to the estimation of the fundamental value of the Hong Kong dollar that is hidden by the target zone peg to the US dollar. We also estimate the implied maturity and explain how this parameter serves as direct proxy for target zone credibility.