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Roseline · 2020年04月04日

问一道题:NO.PZ2019070101000108

问题如下:

Which of the following statements is an advantage of the implied volatility method in estimating future volatility?

选项:

A.

The implied volatility model reacts immediately to changing market conditions.

B.

The implied volatility model is not model dependent.

C.

The implied volatility is constant through time.

D.

The implied volatility is biased upward and is therefore more conservative.

解释:

The only advantage listed is that the implied volatility model reacts immediately to changing market conditions. Forecast models based on historical data require time to adjust to market events. Disadvantages include the following: (1) implied volatility is model dependent;(2) a major assumption of the model is that asset follows a continuous time lognormal diffusion process and are assumed to be constant but that implied volatility varies through time; and (3) implied volatility is biased upward.

老师好,D选项,为什么Implied Volatility is biased upward?

1 个答案

袁园_品职助教 · 2020年04月07日

同学你好!

这里是从实证经验中得到的结论,有印象就可以了,具体关于 implied volatility 的结论我们在二级里会再学习。

可以简单理解为资产价格并不是向 BSM 模型里假设的那样是符合 lognormal 分布的,而是有更多 loss 情况的发生,所以实际上 option 的价格要比 BSM 模型里算出来的要高,这样用 BSM 反推 volatility 的时候 implied volatility 就更大了。

magickame · 2021年10月28日

这个理论听上去有点不合理,如果实际有更多loss发生,实际价格波动应该更大,怎么反而会比BSM模型理想正态分布推算出来的波动率小?