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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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458 14. Gestion <strong>de</strong> Portefeuilles multimoments <strong>et</strong> équilibre <strong>de</strong> marché<br />

where Sn <strong>de</strong>notes the s<strong>et</strong> of agents, among all the agents, who follow the optimiz<strong>at</strong>ion stragtegy with respect<br />

to ρα(n). Thus, the total <strong>de</strong>mand of ass<strong>et</strong> i is<br />

Di = <br />

N φn · Di(n), (124)<br />

n<br />

= N <br />

φn · ˜wi(n) <br />

W (p) · (1 − w0(p)), (125)<br />

n<br />

where N is the total number of agents. This finally yields the total <strong>de</strong>mand D for all ass<strong>et</strong>s and for all agents<br />

D = <br />

Di, (126)<br />

i<br />

p∈Sn<br />

= N <br />

φn · ˜wi(n) <br />

W (p) · (1 − w0(p)), (127)<br />

i<br />

= N <br />

n<br />

n<br />

φn<br />

p∈Sn<br />

<br />

W (p) · (1 − w0(p)), (128)<br />

p∈Sn<br />

since <br />

i ˜wi(n) = 1, for every n. Thus, s<strong>et</strong>ting<br />

<br />

γn = φn p∈Sn <br />

n φn<br />

<br />

p∈Sn<br />

W (p) · (1 − w0(p))<br />

, (129)<br />

W (p) · (1 − w0(p))<br />

the mark<strong>et</strong> portfolio is the weighted sum of the mean-ρα(n) optimal portfolios Πn:<br />

w m i = Si<br />

S<br />

= Di<br />

D<br />

<br />

= γn · ˜wi(n) . (130)<br />

34<br />

n

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