31.05.2014 Views

Processus de Lévy en Finance - Laboratoire de Probabilités et ...

Processus de Lévy en Finance - Laboratoire de Probabilités et ...

Processus de Lévy en Finance - Laboratoire de Probabilités et ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Conclusions and perspectives<br />

In the first part of this thesis we have solved, using <strong>en</strong>tropic regularization, the ill-posed problem<br />

of calibrating an expon<strong>en</strong>tial Lévy mo<strong>de</strong>l to options data and proposed a stable numerical<br />

m<strong>et</strong>hod for computing this solution. Applying our m<strong>et</strong>hod to prices of in<strong>de</strong>x options allowed us<br />

to estimate the risk-neutral Lévy measures, implied by mark<strong>et</strong> prices. This object is the analog,<br />

for expon<strong>en</strong>tial Lévy mo<strong>de</strong>ls, of implied volatility, used in the Black-Scholes framework. Our<br />

empirical results allow to make a number of important conclusions. First, using an expon<strong>en</strong>tial<br />

Lévy mo<strong>de</strong>l one can calibrate with high precision the prices of a s<strong>et</strong> of options with common<br />

maturity. Moreover, high quality of calibration is achieved already by using finite-int<strong>en</strong>sity Lévy<br />

processes. Therefore, from the point of view of option pricing the imperative for using more<br />

complex infinite-int<strong>en</strong>sity mo<strong>de</strong>ls is not clear. The third conclusion is that ev<strong>en</strong> in the nonparam<strong>et</strong>ric<br />

s<strong>et</strong>ting it is impossible, using an expon<strong>en</strong>tial Lévy mo<strong>de</strong>l, to calibrate accurately<br />

the prices of stock in<strong>de</strong>x options of several maturities at the same time: options of differ<strong>en</strong>t<br />

maturities produce differ<strong>en</strong>t implied Lévy measures. This confirms the observation already ma<strong>de</strong><br />

by several authors [13, 68] that the framework of expon<strong>en</strong>tial Lévy mo<strong>de</strong>ls is not suffici<strong>en</strong>tly<br />

flexible to reproduce the term structure of implied volatilities correctly.<br />

In view of the above conclusions, we plan to continue the line of research initiated by this<br />

thesis, by ext<strong>en</strong>ding its results to mo<strong>de</strong>ls of stock price behavior that do allow to <strong>de</strong>scribe the<br />

<strong>en</strong>tire term structure of implied volatilities, e.g. mo<strong>de</strong>ls based on additive processes (processes<br />

with in<strong>de</strong>p<strong>en</strong><strong>de</strong>nt but not stationary increm<strong>en</strong>ts) and hybrid mo<strong>de</strong>ls including both jumps and<br />

stochastic volatility. The second important direction of future research is to investigate the<br />

impact of our calibration m<strong>et</strong>hodology on the m<strong>et</strong>hods of hedging in pres<strong>en</strong>ce of jumps in stock<br />

prices.<br />

In the second part of this thesis we introduced the notion of Lévy copula, providing a<br />

187

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!