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1111111117 · 2025年01月25日

这题不知道liability的convexity,要怎么确保选的convexity大于它?

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NO.PZ201812020100000407

问题如下:

Which of the portfolios in Exhibit 1 best minimizes the structural risk to a single-liability immunization strategy?

选项:

A.

Portfolio 1

B.

Portfolio 3

C.

Portfolio 4

解释:

C is correct.

Structural risk to immunization arises from twists and non-parallel shifts in the yield curve. Structural risk is reduced by minimizing the dispersion of cash flows in the portfolio, which can be accomplished by minimizing the convexity for a given cash flow duration level. Because Portfolio 4 has the lowest convexity compared with the other two portfolios and also has a Macaulay duration close to the liability maturity of nine years, it minimizes structural risk.

这题不知道liability的convexity,要怎么确保选的convexity大于它?是不是这种都直接默认选最小的,如果题目没给liability的convexity

1 个答案

发亮_品职助教 · 2025年01月26日

这道题是单期负债匹配(single liability)。

单期负债匹配里面,不用比较,资产的convexity一定是大于负债convexity的,这是100%成立的。


原因是:单期负债,负债只有一笔cash flow,这相当于是零息债券。而在duration一样的债券里面,零息债券的convexity是最小的。因为convexity与现金流的分散程度成正比,零息债券只有一笔现金流,现金流最为集中,所以其convexity最小。


构建single-liability duraiton matching时,已经构建好了资产的Macaulay duraiton等于负债的Macaulay duration。两者duration一致,负债是零息债券,其convexity最小,资产的convexity一定大于等于负债的convexity。

只有当资产使用零息债券时,其convexity才等于负债的convexity。


一般资产都是付息债券,可知,资产convexity一定大于负债的convexity。

此时,直接选convexity最小的资产即可!convexity最小的structural risk最小,匹配越安全。


相当于single liability这里,资产的convexity大于负债的convexity是100%成立的默认条件,我们自己选的时候只需找convexity最小的资产即可。


而在multiple libilities的duration-mathing里,资产与负债的convexity不存在绝对的大小关系。所以要先找asset convexity > liability convexity的(先找到符合duraiton-matching条件的),然后再找Minimize asset convexity来降低structural risk。