10. Portfolio Theory - Principles & Limitations Flashcards
A. Management of portfolio risk (page 2)
Modern Portfolio Theory (MPT):
- is concerned with the way in which portfolios can be constructed to maximise returns and minimise risks.=
- says that all assets need to be considered in respect of how they interact with each other
- assumes that investors are risk adverse, choosing a less risky investment if offered the choice
A1. Defining risk through standard deviation (pages 2 & 3)
Standard Deviation:
- the most commonly used measure of risk is the volatility of returns or Standard Deviation
- measures how widely the actual return on an investment varies around its average or expected return
- the higher the standard deviation the higher the risk
USALLY DESIGNATED BY THE GREEK LETTER SIGMA:
- an o with a high tail to the right
A1. Defining risk through standard deviation (pages 2 & 3)
CONTINUED
Example of Mean of 8% and Standard Deviation of 5%:
Returns can be expected to fall within 1 Standard Deviation 68% of the time:
- between 3% and 13% (Mean 8% +/- 5%)
Returns can be expected to fall within 2 Standard Deviations 95% of the time:
- between -2% and 18% (Mean 8% +/- 2 x 5%)
SKEWING
- POSITIVE SKEW (peak of curve to LEFT OF CENTRE)
- NEGATIVE SKEW (peak of curve to RIGHT of centre)
A2. Managing risk (page 3)
Normally buying low-risk assets will give a low-risk portfolio, but leads to low returns.
More attractive approach is to buy risky-assets and reduce the risk in two ways:
- hedging out risk
- diversifying portfolio holdings
A2A. Hedging (page 3)
Hedging means:
- protecting an existing investment position by taking another position that will increase in value
This can be acheived using derivatives:
- selling FTSE 100 futures contracts
- buying FTSE 100 put options
A2B. Diversification of risk (pages 3 & 4)
Holding a mixture of investment types, the portfolio is diversified and takes of advantage of the various assets when they perform well in certain market conditions.
A2C. Correlation (pages 4 & 5)
The effectiveness of diversification is dependant on the degree of correlation between the returns of different assets in the portfolio.
Correlation is a number between +1 and -1
- Closer to 1 is positive (move in same direction)
- Close to 0 is no relationship
- Closer to -1 is negative (move in opposite directions)
Most effective diversification comes from combining investments that are negatively correlated.
A2C. Correlation (pages 4 & 5)
CONTINUED
POSITIVE CORRELATION: the assets move up and down together. They are affected by the same things.
NEGATIVE CORRELATION: the assets move in opposite directions to each other.
NO CORRELATION: the shares/assets are not related to each other.
A2C. Correlation (pages 4 & 5)
CONTINUED
Diversification can be acheived by:
- HOLDING DIFFERENT ASSET CLASSES
- CHOOSING COMPANIES FROM DIFFERENT SECTORS
- INCLUDING OVERSEAS COMPANIES
B. The efficient frontier (page 5)
The relationship between the return that can be expected from a portfolio and the risk of the portfolio as measured by standard deviation.
B1. Constructing an efficient frontier (page 6)
Shows the best return that can be expected for a given level of risk.
Inputs to the models are:
- return of each asset class
- standard deviation of each asset’s returns
- correlation between each pair of assets’ returns
RISK - LEFT/RIGHT (standard deviation)
RETURN - UP/DOWN
B2. Limitations to using an efficient frontier (pages 6 & 7)
Limitations to using an efficient frontier:
- assumes that standard deviation is the correct measure of risk
- assets have normally distributed returns
- difficult to say which portfolio investors would prefer based solely on their attitude to risk
- inputs for risk and correlation between investors rely on historic data which may be unstable
- model does not include transaction costs
- assumes the underlying portfolios in each asset class are index funds
C. Capital asset pricing model (CAPM) (page 7)
C1. Systematic and non-systematic risk (pages 7 & 8)
SYSTEMATIC RISK (MARKET RISK)
- the risk that affects the market as a whole
- cannot be avoided
- measured by Beta (the volatility of stock relavant to the market)
NON-SYSTEMATIC RISK (INVESTMENT SPECIFIC)
- unique to a particular company or stock
- can be eliminated by holding a diversified portfolio
C2. Beta (page 8)
The Market has a Beta of 1.
The Beta of an individual security reflects the extent to which its return moves up or down relevant to the Market.
INDIVIDUAL SHARE’S BETA:
- Equal to 1: it’s return moves exactly the same as the Maket’s. Market goes up 10%, so does the share
- More than 1: exagerates the market’s movements, so more volatile. Market goes up, share goes up more
- Less than 1 (but more than 0): opposite to more than 1. Market goes down, share goes down but by less than the Market
C3. CAPM equation (pages 8 & 9)
CAPM derives the theoretical expected return for a security as a combination of the:
- return on a risk-free asset (such as a treasury gilt)
- risk premium (the compensation for holding a risky investment)
CAPM Equation:
E(Ri) = Rf + Bi (Rm - Rf)
E(Ri) = expected return on the risky investment
Rf = rate of return on risk-free asset
Rm - expected return of model portfolio
Bi = beta (sensitivity of investment to overall market)
(Rm - Rf) = market risk premium
Bi (Rm - Rf) = risk premium of the risky investment
Example:
- Share has beta of 1.4
- Treasury Bill expected return of 3.5%
- expected return on the portfolio Market of 8%
E(Ri) = 3.5 + 1.4 (8 - 3.5)