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luojy · 2024年05月08日

答案又错了?

NO.PZ2022122801000025

问题如下:

Remington and Montgomerynext meet with client Katherine Winfeld. The firm had established Winfeld’scurrent asset allocation on the basis of reverse optimization using theinvestable global market portfolio weights with further adjustments to reflectWinfeld’s views on expected returns.

The model on whichWinfeld’s current asset allocation is based is best characterized as: (2019 moc

选项:

A.

mean–variance optimization.

B.

Black–Litterman.

C.

reverse optimization.

解释:

B is correct. Winfeld’s current asset allocation is most likely based on the Black–Litterman model. Black–Litterman starts with the excess returns produced from reverse optimization, which commonly uses the observed market-capitalization value of the assets or asset classes of the global opportunity set. It then alters the reverse-optimized expected returns that reflect an investor’s own distinctive views yet still behaves well in an optimizer.

A is incorrect. Asset allocations using mean–variance optimization tend to be concentrated in a subset of the available asset classes. Winfeld’s portfolio will be allocated to all or most of the asset classes through the reverse-optimization process followed by adjustments reflecting the investor’s views.

C is incorrect. Reverse optimization takes as its inputs a set of asset allocation weights that are assumed to be optimal and, with covariances and the risk aversion coefficient, solves for expected returns. The starting weights are commonly the observed market capitalization value of the assets or asset classes of the global opportunity set. The asset allocation using reverse optimization would not take into account the investor’s own views.

这题描述的输出变量就是E(R) 呀,不是reverse optimization吗? black litterman的输出变量是weight

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lynn_品职助教 · 2024年05月09日

嗨,爱思考的PZer你好:


这题描述的输出变量就是E(R) 呀,不是reverse optimization吗? black litterman的输出变量是weight


BL也要先求出E(R)的,BL模型是通过已知权重、标准差、相关性,反向求出implied return,这里的权重通常使用的是资产的市值权重,所以求出来的implied return更稳定、更准确,因此得出的资产配置分散化效果也更好。但是已知的那些inputs是很难得到的。


reverse optimization与Black-Litterman之所以比MVO好,是由于这两种方法是通过已知权重、标准差、相关性,反向求出implied return,这里的权重通常使用的是资产的市值权重,所以求出来的implied return更稳定、更准确,因此得出的资产配置分散化效果也更好。


只是BL还有第二步,即加入分析师的观点,结论对观点还是很敏感的,会出现一些极端情况。


原版书的完整表述是:The mathematical details of the Black–Litterman model are beyond the scope of this reading, but many practitioners have access to asset allocation software that includes the Black–Litterman model.

大意是:Black–Litterman模型的数学细节超出了本文的阅读范围,但我们可以使用一些资产配置软件来构建Black–Litterman模型

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