November 15th, 2006, 5:54 pm
A Parsimonious Framework for Pricing Future Generation Structured Notes The objective is to build a versatile framework that can be quickly readjusted to price all kinds of complex structured notes, including interest rate-, FX-, equity-, and commodity-linked notes. Possibly with path-dependent features. Possibly with callable features.This sounds like Holy Grail. However, here are some mitigating circumstances:a) it is not a front-office tool, it is a middle-office tool to run infrequently (say, once a week) in order to tune a very rough approximations used for future risk exposure computations, to improve collateral management, and to check on front-office pricing systemb) thus, 3% relative error in pricing is, perhaps, acceptablec) thus, precision on sensitivities is not requiredd) this tool will only be run for problem structures, as a matter of reconciliation between different systems.The framework should be sufficiently versatile and economical, as resources to build and thencustomize, calibrate and run the tool are very limited. Bottom line: when new type of structure, say FX-based targeted redemption note, comes along customization of pricing function should be straightforward and quick.Here are several model design decisions and issues I want to discuss but I welcome any comment from the Quant community.Model 1. For short-term LIBOR rate and/or commodity price: Several forward price processes on the underlying asset are run simultaneously. As forward matures, its price is fixed thereafter. SABR is adopted for each forward process until maturity with parameters calibrated to volatility smile at maturity point (where available). All correlations between forwards, their volatilities, and cross are historical and fixed For FX: spot lognormal process: Run with 2 short-term rates for 2 currencies, see the process above, with correlated diffusion terms. FX drift at each step of simulation is determined by the simulated short rate differential. FX instantaneous volatility is fixed and along with all correlations is determined from history. For equity: spot lognormal process: with r-q drift and historical volatility uncorrelated to fixed income risk factors or spot SABR process: if rich dataset of implied volatility surfaces is available for calibrationMy impression is that the alternatives are either not versatile enough or very expensive to calibrate properly (like local volatility model, if developed from scratch). What do you think?Model 2. Sub-optimal exercise decision in the space of Monte-Carlo scenarios generated by the defined above simulation process. Longstaff-Schwartz technique used with quadratic polynomial functions over the total set of simulated risk factors.Issues in question:1) Should BGM drift formula change when volatility becomes SABR-like ?2) Is there any consensus on how to extrapolate volatility of volatility outside the time framewhere the smile is available to calibrate SABR? Any particular parametric form?3) Are there better sub-optimal exercise techniques than Longstaff-Schwartz, and in particular for SABR-like simulations of risk factors? Any pointers here?4) Any papers on how well this technique works for path-dependent callables, also what about the degree of polynomials used here, do quadratic polynomials work ok ? Thank you