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statistique, théorie et gestion de portefeuille - Docs at ISFA

statistique, théorie et gestion de portefeuille - Docs at ISFA

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318 9. Mesure <strong>de</strong> la dépendance extrême entre <strong>de</strong>ux actifs financiers<br />

increase of the idiosyncr<strong>at</strong>ic vol<strong>at</strong>ility suggests th<strong>at</strong> the main source of risk in such a period does<br />

not consist in the <strong>de</strong>pen<strong>de</strong>nce b<strong>et</strong>ween ass<strong>et</strong>s but r<strong>at</strong>her in their instrinsic fluctu<strong>at</strong>ions measured<br />

by the idiosyncr<strong>at</strong>ic volality.<br />

Our study has focused on the <strong>de</strong>pen<strong>de</strong>nce b<strong>et</strong>ween different risks. In fact, our theorem can obviously<br />

be applied to extreme temporal <strong>de</strong>pen<strong>de</strong>nces, when the variable follows an autoregressive process.<br />

This should provi<strong>de</strong> an estim<strong>at</strong>e of the probability th<strong>at</strong> a large loss (respectively gain) is followed<br />

by another large loss (resp. gain) in the following period. Such inform<strong>at</strong>ion is very interesting in<br />

investment and hedging str<strong>at</strong>egies.<br />

19

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