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中二 · 2020年01月30日

问一道题:NO.PZ2016070202000016 [ FRM II ]

问题如下:

In early 2000, a risk manager calculates the VAR for a technology stock fund based on the past three years of data. The strategy of the fund is to buy stocks and write out-of-the-money puts. The manager needs to compute VAR. Which of the following methods would yield results that are least representative of the risks inherent in the portfolio?

选项:

A.

Historical simulation with full repricing

B.

Delta-normal VAR assuming zero drift

C.

Monte Carlo style VAR assuming zero drift with full repricing

D.

Historical simulation using delta equivalents for all positions

解释:

D is correct.

Because the portfolio has options, methods A or C based on full repricing would be appropriate. Next, recall that technology stocks had a big increase in price until March 2000. From 1996 to 1999, the NASDAQ index went from 1,300 to 4,000. This creates a positive drift in the series of returns. So, historical simulation without an adjustment for this drift would bias the simulated returns upward, thereby underestimating VAR.

老师,我刚听完市场风险section1时做到这道题,说实话不太理解,能不能解释一下每个选项?

1 个答案

品职答疑小助手雍 · 2020年02月04日

同学你好,当时科技股全在大涨,相对于大盘有更高的收益,即return drift upward,因此要对漂移进行处理,否则这时候会计量的var会小。assuming zero drift就是不对漂移做处理。 题目问哪种方法最不合适,

full pricing(直接重新估值,不借助过去有偏差的数据)都差不多可以用,

D选项用historical simulation在互联网泡沫的背景下肯定是高估的,而delta normal的VAR至少还是假设了基础资产收益呈正态分布的delta*(u-z*sigama),相对而言,D比B高估的更直接。

所以选D