问题如下:
The benchmark portfolio is the S&P 500. Which of the following three portfolios can be combined with the benchmark portfolio to produce the highest combined Sharpe ratio?
选项:
A. Portfolio A
B. Portfolio B
C. Portfolio C
解释:
B is correct.
The active portfolio that is optimal is the portfolio with the highest Information ratio, the ratio of active return to active risk. The IRs for the three active portfolios are:
= 1.0/10.0 = 0.10
= 0. 5/3.0 = 0.167
= 0/2.0 = 0.00
Portfolio B has the highest IR and is the best active portfolio; it is therefore the best portfolio to combine with the benchmark.
考点:Sharpe ratio
解析:,benchmark的Sharpe ratio对于每个Combined portfolio都相同,因此information ratio最大的组合将会得到最大的Combined Sharpe ratio。
ABC组合的IR分别为:0.1,0.167,0。 组合B的IR最大,因此, combined Sharpe ratio 最大。
讲义里说SR combine等于SR portfolio,为什么不能直接用portfolio A的SR最大来判断?