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旧人序 · 2022年07月19日

请问只看cvar吗?var用不用看?

* 问题详情,请 查看题干

NO.PZ201909280100001103

问题如下:

Based on Exhibit 2, which alternative portfolio should Gension recommend for the fund given Smittand’s stated three goals?

选项:

A.

Portfolio A

B.

Portfolio B

C.

Portfolio C

解释:

A is correct. Among the three portfolios, Portfolio A minimizes the probability of triggering the primary lender’s loan covenant, which is the highest-priority goal, because it has the lowest one-year 99% CVaR, –19.4%. Portfolio A also has the lowest probability of purchasing power impairment over a 10-year horizon (2.5%). While Portfolio A has the lowest probability of achieving a real return target of 6% over a 10-year horizon (56.1%), that is the least important goal to be met. Therefore, Gension should recommend Portfolio A for the fund.

B is incorrect because Portfolio B has a one-year 99% CVaR of –20.6%, which crosses the loan covenant threshold of a 20% loss. Portfolio A is the only one that satisfies the most important goal and is the portfolio least likely to trigger the loan covenant. Since Portfolio B does not achieve the most important goal of minimizing the probability of triggering the primary lender’s loan covenant, Portfolio B should not be the recommended portfolio.

C is incorrect because despite the fact that Portfolio C has the highest probability of meeting the 6% real return over a 10-year horizon, 61.0%, it also has a one-year 99% CVaR of –22.7% and thus the highest probability of triggering the loan covenant. Portfolio A is the only one that satisfies the most important goal and is the portfolio least likely to trigger the loan covenant. Since Portfolio C does not achieve the most important goal of minimizing the probability of triggering the primary lender’s loan covenant, Portfolio C should not be the recommended portfolio.

这个题的核心是这句话


然后是弄明白CVaR是什么意思,一年期 99% CVaR:如果回报低于 99% VaR 阈值时的预期回报。具体解释就是先说VaR,这个是指比如在99%的可能下的最差表现,可是问题是万一出现那百分之一呢?于是有了这个一年期 99% CVaR,就是用来研究在极端情况下(就是那个1%)可能产生的最差情况。

而这个题的表2,portfolio B和C都在CVaR情况下跌幅超过20%。于是只剩下了portfolio A了。

好几道题中都是var和cvar都给,var用不用看?

3 个答案
已采纳答案

伯恩_品职助教 · 2022年08月01日

嗨,努力学习的PZer你好:


嗯,好的,首先要先理解,var和cvar。

CVaR 即条件风险价值,是由RockafeUar和Uryasev等于1997年提出的一种较VaR更优的风险计量技术,其含义为在投资组合的损失超过某个给定VaR值的条件下,该投资组合的平均损失值。

Var是研究在99%的情况下最大亏损的可能性,那万一是那1%怎么办?这里就引出了 CVaR,即那1%的情况下最大亏损是多少。

这个题在这里明确说明是要保证不能触发loan covenant,那就是说尽可能要降低概率,VAR只考虑了99%的情况,而cvar考虑剩下的最极端的不好的1%的情况,也就是说这1%的概率不发生,基本就不会发生。所以这里关键看cvar。如果说题目问题说的是大概率比如99%的情况,就看var。如果是最小可能性就是极端情况也不能,就看cvar

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旧人序 · 2022年08月01日

噢!老师,我明白了!还是得理解好题目要求,“保证不能触发loan covenant”所以要用CVAR。Var 某个分位数的点数据,Cvar相当于累积数据,求和,var点数据左边极端情况求和了。所以还是题目,问var就用var,向这题问的“保证不能触发loan covenant”就是在说cvar,所以筛选时候看cvar!明白了!谢谢老师讲解!

伯恩_品职助教 · 2022年08月01日

嗨,爱思考的PZer你好:


不客气

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伯恩_品职助教 · 2022年07月19日

嗨,从没放弃的小努力你好:


关键是根据题目中的条件,如果题目问比如99%情况下(或者98%的情况下等)就是用var,如果是问1%情况下就是cvar,关键看题目

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加油吧,让我们一起遇见更好的自己!

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