BKM Chapter 9 Flashcards
Main uses for CAPM (2)
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- benchmark ROR for evaluating potential investments
2. estimating the expected return on assets not yet traded in the marketplace
CAPM assumptions about individual behavior (3)
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all investors:
- are mean-variance optimizers
- have investment horizon = 1 period
- use identical input lists (b/c all relevant info is publicly available)
CAPM assumptions about market structure (4)
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- all assets are publicly held & traded on public exchanges
- investors can borrow/lend at the risk-free rate and short positions are allowed
- no taxes
- no transaction costs
Categories of CAPM assumptions (2)
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- individual behavior
2. market structure
Key results of CAPM (3)
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all investors arrive at identical efficient frontiers (based on assumptions)
> > all have identical CALs
> > all have identical optimal risky portfolios = market portfolio
Each investor’s CAL under CAPM
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CAL = CML
Reason portfolio managers hold risky portfolios <> market portfolio in reality
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b/c of differences in input lists
Which stocks are included in the market portfolio under CAPM?
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all stocks
Expected risk premium of the market portfolio under CAPM (alternative formula)
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E[R(M)] = A-bar * sigma^2(M)
where A-bar = average risk aversion of all investors and y* = 1
CAPM assumption about expected returns of individual securities
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an individual asset’s risk premium is determined by it’s contribution to total risk
Market price of risk
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reward-to-risk ratio for the efficient portfolio (= market portfolio)
= market risk premium / market variance
Classic CAPM formula (aka mean-beta relationship)
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E[r(i)] = risk-free rate + beta * market risk premium
What does beta measure?
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measures the contribution of the individual asset to the variance of the market portfolio
Difference between CAPM and the single-index model and optimal risky portfolios
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CAPM assumes every stock has alpha = 0
with rebalancing (so all alpha’s = 0) both will end at the same optimal risky portfolios = market portfolio
Mean-beta relationship and the security market line (SML) - slope, y-intercept, and points of interest
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plots expected returns on the y-axis and beta on the x-axis
SML has slope = market risk premium
y-intercept = risk-free rate
E[r(M)] = return when beta = 1
individual stocks fall above/below the SML depending on their alphas (positive > above)
Alpha
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alpha = difference b/w an individual stock’s expected return and the SML (required return from CAPM)
alpha = investor forecast return - CAPM return
Interpretation of the SML
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required return under CAPM for the associated beta
all fairly priced securities live on the SML
Difference b/w the SML and the CML
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SML can be used for individual assets and efficient portfolios vs. CML which can only be used for efficient portfolios (b/c the x-axis is standard deviation, which isn’t appropriate for individual assets)
Reasons short positions are harder to take than long positions (3)
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- large amount of collateral needed
- limited supply may restrict short positions
- short positions are prohibited for some investment companies