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In terms of the measures presented it turns out that historical simulation
is not as bad as one would expect for such a simplistic model - which
makes no attempt to capture the dynamics of the market and which is
based entirely on the series x(P) without referring to the
characteristics of the individual risk factors x(k). It has reasonable
results in terms of the digital measures but has very bad quality
in terms of the degree of exceedence as reported in figures 4 and 5.
We believe that by introducing smoothing in the conditional distribution
determined from the 250 day empirical distribution - with the constraint
that the probability density must monotonically decrease away from
the center - the performance of this model can be considerably improved.
If in addition the smoothed 250 day empirical distribution based on
Xt (expression
) could be modulated so as to confirm to
the variance of a GARCH(1,1) process (optimized with tail emphasis)
then the resultant model may be extremely powerful. The caveat of such
a scheme however is the complexity introduced in the portfolio function
if this methodology is employed in the usual way - where the stochastic
process predicts each series x(k) rather than directly predicting
the portfolio series x(P). For now, we leave this proposal of such a
hybrid approach - mixing historical simulation and stochastic methods -
as food for thought for future investigations.
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