1 PORTFOLIO ANALYSIS
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PORTFOLIO ANALYSIS
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THE EFFICIENT SET THEOREM
• THE THEOREM– An investor will choose his optimal portfolio
from the set of portfolios that offer• maximum expected returns for varying levels of
risk, and
• minimum risk for varying levels of returns
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THE EFFICIENT SET THEOREM
• THE FEASIBLE SET– DEFINITION: represents all portfolios that
could be formed from a group of N securities
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THE EFFICIENT SET THEOREM
THE FEASIBLE SETrP
P0
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THE EFFICIENT SET THEOREM
• EFFICIENT SET THEOREM APPLIED TO THE FEASIBLE SET– Apply the efficient set theorem to the feasible set
• the set of portfolios that meet first conditions of efficient set theorem must be identified
• consider 2nd condition set offering minimum risk for varying levels of expected return lies on the “western” boundary
• remember both conditions: “northwest” set meets the requirements
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THE EFFICIENT SET THEOREM
• THE EFFICIENT SET– where the investor plots indifference curves and
chooses the one that is furthest “northwest”– the point of tangency at point E
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THE EFFICIENT SET THEOREM
THE OPTIMAL PORTFOLIO
E
rP
P0
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CONCAVITY OF THE EFFICIENT SET
• WHY IS THE EFFICIENT SET CONCAVE?– BOUNDS ON THE LOCATION OF
PORFOLIOS– EXAMPLE:
• Consider two securities– Ark Shipping Company
» E(r) = 5% = 20%– Gold Jewelry Company
» E(r) = 15% = 40%
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CONCAVITY OF THE EFFICIENT SET
P
rP
A
G
rA = 5
A=20
rG=15
G=40
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CONCAVITY OF THE EFFICIENT SET
• ALL POSSIBLE COMBINATIONS RELIE ON THE WEIGHTS (X1 , X 2)
X 2 = 1 - X 1
Consider 7 weighting combinations
using the formula
22111
rXrXrXrN
iiiP
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CONCAVITY OF THE EFFICIENT SET
Portfolio return
A 5
B 6.7
C 8.3
D 10
E 11.7
F 13.3
G 15
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CONCAVITY OF THE EFFICIENT SET
• USING THE FORMULA
we can derive the following:
2/1
1 1
N
i
N
jijjiP XX
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CONCAVITY OF THE EFFICIENT SET
rP P=+1 P=-1
A 5 20 20
B 6.7 10 23.33C 8.3 0 26.67D 10 10 30.00E 11.7 20 33.33F 13.3 30 36.67G 15 40 40.00
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CONCAVITY OF THE EFFICIENT SET
• UPPER BOUNDS– lie on a straight line connecting A and G
• i.e. all must lie on or to the left of the straight line
• which implies that diversification generally leads to risk reduction
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CONCAVITY OF THE EFFICIENT SET
• LOWER BOUNDS– all lie on two line segments
• one connecting A to the vertical axis
• the other connecting the vertical axis to point G
– any portfolio of A and G cannot plot to the left of the two line segments
– which implies that any portfolio lies within the boundary of the triangle
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CONCAVITY OF THE EFFICIENT SET
G
upper bound
lower bound
rP
P
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CONCAVITY OF THE EFFICIENT SET
• ACTUAL LOCATIONS OF THE PORTFOLIO– What if correlation coefficient (ij ) is zero?
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CONCAVITY OF THE EFFICIENT SET
RESULTS:
B = 17.94%
B = 18.81%
B = 22.36%
B = 27.60%
B = 33.37%
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CONCAVITY OF THE EFFICIENT SET
ACTUAL PORTFOLIO LOCATIONS
CD
F
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CONCAVITY OF THE EFFICIENT SET
• IMPLICATION:
– If ij < 0 line curves more to left
– If ij = 0 line curves to left
– If ij > 0 line curves less to left
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CONCAVITY OF THE EFFICIENT SET
• KEY POINT
– As long as -1 < the portfolio line curves to the left and the northwest portion is concave
– i.e. the efficient set is concave
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THE MARKET MODEL
• A RELATIONSHIP MAY EXIST BETWEEN A STOCK’S RETURN AN THE MARKET INDEX RETURN
where intercept term
ri = return on security
rI = return on market index I
slope term
random error term
iIIiiIi rr 1
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THE MARKET MODEL
• THE RANDOM ERROR TERMS i, I
– shows that the market model cannot explain perfectly
– the difference between what the actual return value is and
– what the model expects it to be is attributable to i, I
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THE MARKET MODEL
i, I CAN BE CONSIDERED A RANDOM
VARIABLE
– DISTRIBUTION:• MEAN = 0
• VARIANCE = i
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DIVERSIFICATION• PORTFOLIO RISK
TOTAL SECURITY RISK: i
• has two parts:
where = the market variance of index returns
= the unique variance of security i returns
2222iiiIi
22 iI2i
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DIVERSIFICATION
• TOTAL PORTFOLIO RISK– also has two parts: market and unique
• Market Risk– diversification leads to an averaging of market risk
• Unique Risk– as a portfolio becomes more diversified, the smaller will
be its unique risk
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DIVERSIFICATION• Unique Risk
– mathematically can be expressed as
N
iiP N1
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2 1
NNN
222
21 ...1