361 The Black-Litterman Approach to Portfolio Optimization
The δ introduced in column B of the preceding fi gure indicates
Joanna’s deviation from the Black-Litterman base case. In this example,
Joanna thinks that GM will have a monthly return 0.14 percent higher
than the market’s return of 0.96 percent (cell B24). Because of the co-
variance between asset returns, this change means that the HD return
she expects is 1.11 percent:
rr
r
r
HD, opinion adjusted HD, market
HD, GM
HD
GM
Cov( )
Var
=+ =
()
.δ 1 11%%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
ABCDEFGHIJK
L
Anticipated benchmark return 1.00% <
--
=12%/12
Current t-bill rate 0.40%
General
Motors
GM
Home
Depot
HD
International
Paper
IP
Hewlett-
Packard
HPQ
Altria
MO
American
Express
AXP
Alcoa
Aluminum
AA
DuPont
DD
Merck
MRK
MMM
Equity value 16.85 73.98 15.92 88.37 153.33 65.66 28.16 38.32 79.51 60.9
Benchmark proportions 2.71% 11.91% 2.56% 14.23% 24.69% 10.57% 4.53% 6.17% 12.80% 9.81%
Variance-covariance matrix
GM HD IP HPQ MO AXP AA DD MRK MMM
GM 0.0116 0.0030 0.0023 0.0041 0.0013 0.0032 0.0046 0.0018 0.0010 0.0014
HD 0.0030 0.0071 0.0018 0.0042 0.0022 0.0033 0.0045 0.0020 0.0002 0.0018
IP 0.0023 0.0018 0.0039 0.0031 0.0001 0.0023 0.0043 0.0021 0.0012 0.0016
HPQ 0.0041 0.0042 0.0031 0.0117 0.0025 0.0048 0.0060 0.0033 0.0019 0.0022
MO 0.0013 0.0022 0.0001 0.0025 0.0076 0.0016 0.0018 0.0009 0.0007 0.0008
AXP 0.0032 0.0033 0.0023 0.0048 0.0016 0.0041 0.0037 0.0019 0.0011 0.0014
AA 0.0046 0.0045 0.0043 0.0060 0.0018 0.0037 0.0091 0.0040 0.0018 0.0024
DD 0.0018 0.0020 0.0021 0.0033 0.0009 0.0019 0.0040 0.0038 0.0016 0.0019
MRK 0.0010 0.0002 0.0012 0.0019 0.0007 0.0011 0.0018 0.0016 0.0065 0.0005
MMM 0.0014 0.0018 0.0016 0.0022 0.0008 0.0014 0.0024 0.0019 0.0005 0.0031
Expected benchmark returns,
no opinions
Analyst
opinion,
delta
Returns
adjusted for
opinions
Optimized
benchmark
proportions
Portfolio
benchmark,
no opinions
0.96% 0.14% GM 1.10% <
--
{=A24:A33+MMULT(B38:K47,B24:B33)} 5.19% GM 2.71%
1.05% 0.00% HD 1.11% 8.23% HD 11.91%
0.77% 0.00% IP 0.86% 7.60% IP 2.56%
1.36% 0.00% HPQ 1.41% 6.60% HPQ 14.23%
1.05% 0.00% MO 1.07% 20.72% MO 24.69%
0.97% 0.00% AXP 1.08% 22.17% AXP 10.57%
1.17% 0.00% AA 1.24% -1.98% AA 4.53%
0.84% 0.00% DD 0.91% 10.67% DD 6.17%
0.77% 0.00% MRK 0.79% 9.54% MRK 12.80%
0.73% 0.00% MMM 0.79% 11.26% MMM 9.81%
Tracking factors: in each row i Cov(r
i
,r
) is divided by Var(r
i
)
GM HD IP HPQ MO AXP AA DD MRK MMM
GM 1.0000 0.2589 0.1999 0.3540 0.1153 0.2788 0.3920 0.1555 0.0829 0.1169
HD 0.4257 1.0000 0.2603 0.5934 0.3119 0.4635 0.6376 0.2834 0.0250 0.2501
IP 0.5985 0.4738 1.0000 0.7940 0.0222 0.5954 1.0994 0.5306 0.3056 0.4063
HPQ 0.3527 0.3594 0.2642 1.0000 0.2162 0.4145 0.5097 0.2791 0.1665 0.1878
MO 0.1769 0.2909 0.0114 0.3328 1.0000 0.2096 0.2351 0.1158 0.0884 0.1046
AXP 0.7843 0.7927 0.5595 1.1704 0.3845 1.0000 0.8956 0.4624 0.2556 0.3270
AA 0.5006 0.4950 0.4690 0.6533 0.1957 0.4066 1.0000 0.4404 0.1938 0.2625
DD 0.4820 0.5343 0.5496 0.8687 0.2342 0.5097 1.0694 1.0000 0.4327 0.5067
MRK 0.1483 0.0272 0.1826 0.2991 0.1032 0.1626 0.2715 0.2497 1.0000 0.0741
MMM 0.4437 0.5772 0.5151 0.7156 0.2588 0.4412 0.7802 0.6202 0.1571 1.0000
Cells J24:J33 contain the array
formula
{=MMULT(MINVERSE(B11:K20),D2
4:D33-
B3)/SUM(MMULT(MINVERSE(B11:K
20),D24:D33-B3))}
ADJUSTING THE BENCHMARK FOR AN ANALYST'S OPINION
In this example the only opinion is about GM