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statistique, théorie et gestion de portefeuille - Docs at ISFA

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Vol<strong>at</strong>ility Fingerprints of Large Shocks:<br />

Endogeneous Versus Exogeneous ∗<br />

D. Sorn<strong>et</strong>te 1,2 , Y. Malevergne 1,3 and J.-F. Muzy 4<br />

1 Labor<strong>at</strong>oire <strong>de</strong> Physique <strong>de</strong> la M<strong>at</strong>ière Con<strong>de</strong>nsée CNRS UMR 6622<br />

Université <strong>de</strong> Nice-Sophia Antipolis, 06108 Nice Ce<strong>de</strong>x 2, France<br />

2 Institute of Geophysics and Plan<strong>et</strong>ary Physics and Department of Earth and Space Science<br />

University of California, Los Angeles, California 90095, USA<br />

3 Institut <strong>de</strong> Science Financière <strong>et</strong> d’Assurances - Université Lyon I<br />

43, Bd du 11 Novembre 1918, 69622 Villeurbanne Ce<strong>de</strong>x, France<br />

4 Labor<strong>at</strong>oire Systèmes Physiques <strong>de</strong> l’Environemment, CNRS UMR 6134<br />

Université <strong>de</strong> Corse, Quartier Gross<strong>et</strong>ti, 20250 Corte, France<br />

email: sorn<strong>et</strong>te@unice.fr, Yannick.Malevergne@unice.fr and muzy@univ-corse.fr<br />

fax: (310) 206 30 51<br />

Forthcoming Risk<br />

Abstract<br />

Finance is about how the continuous stream of news g<strong>et</strong>s incorpor<strong>at</strong>ed into prices. But not all news<br />

have the same impact. Can one distinguish the effects of the Sept. 11, 2001 <strong>at</strong>tack or of the coup<br />

against Gorbachev on Aug., 19, 1991 from financial crashes such as Oct. 1987 as well as smaller<br />

vol<strong>at</strong>ility bursts? Using a parsimonious autoregressive process with long-range memory <strong>de</strong>fined on the<br />

logarithm of the vol<strong>at</strong>ility, we predict strikingly different response functions of the price vol<strong>at</strong>ility to gre<strong>at</strong><br />

external shocks compared to wh<strong>at</strong> we term endogeneous shocks, i.e., which result from the cooper<strong>at</strong>ive<br />

accumul<strong>at</strong>ion of many small shocks. These predictions are remarkably well-confirmed empirically on<br />

a hierarchy of vol<strong>at</strong>ility shocks. Our theory allows us to classify two classes of events (endogeneous<br />

and exogeneous) with specific sign<strong>at</strong>ures and characteristic precursors for the endogeneous class. It also<br />

explains the origin of endogeneous shocks as the coherent accumul<strong>at</strong>ions of tiny bad news, and thus<br />

unify all previous explan<strong>at</strong>ions of large crashes including Oct. 1987.<br />

1 Introduction<br />

A mark<strong>et</strong> crash occurring simultaneously on most of the stock mark<strong>et</strong>s of the world as witnessed in Oct.<br />

1987 would amount to the quasi-instantaneous evapor<strong>at</strong>ion of trillions of dollars. Mark<strong>et</strong> crashes are the<br />

extreme end members of a hierarchy of mark<strong>et</strong> shocks, which shake stock mark<strong>et</strong>s repe<strong>at</strong>edly. Among<br />

∗ We acknowledge helpful discussions and exchanges with E. Bacry and V. Pisarenko. This work was partially supported by the<br />

James S. Mc Donnell Found<strong>at</strong>ion 21st century scientist award/studying complex system.<br />

1<br />

137

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