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"Frontmatter". In: Analysis of Financial Time Series

"Frontmatter". In: Analysis of Financial Time Series

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EXTREME VALUE THEORY 273shows that the tail index k does not depend on the time interval <strong>of</strong> r t . That is, the tailindex (or equivalently the shape parameter) is invariant under time aggregation. Thissecond feature <strong>of</strong> the limiting distribution becomes handy in the VaR calculation.The extreme value theory has been extended to serially dependent observations{r t } n t=1provided that the dependence is weak. Berman (1964) shows that the sameform <strong>of</strong> the limiting extreme value distribution holds for stationary normal sequencesprovided that the autocorrelation function <strong>of</strong> r t is squared summable (i.e., ∑ ∞i=1 ρi 2

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