Quiz 2 Flashcards
When we add a risk free asset to our portfolio, why does the variance equation not change?
No change = The variance equation remains the same as the level of risk is determined by the risky assets. In other words the risk free asset does not add risk.
What is the one fund theorem?
What does the one fund theorem suggest?
One fund theorem = States that when a risk-free asset exists, that the entire set of efficient portfolios can be created by combining together one fund of risky assets, T, with the risk-free asset. The fund T is the tangency portfolio
Suggests = that an investment management companys only needs to create on fund of risky assets for all of their clients
What is Tobins seperation theorem?
Tobins seperation theorem = states that an individuals investment decision can be separated into two parts
1: Determine tangency portfolio
2: Combine T with the risk-free asset in such a way that utility is maximised
What do we mean by solve the markowitz problem?
Solve markowitz = find the weights of the assets which would achieve the specified portfolio Mu
What do we mean when we say no borrowing exists at the risk free rate?
What does this imply for the one fund theorem?
No borrowing = we are referring to the fact that a portfolio consisting of risky assets and a risk free asset can achieve a higher return than the tangency portfolio if we place a negative weight into the risk free asset (and as such are borrowing) and thus continue in a straight line along the efficient frontier. Now when no borrowing exists we are unable to do this and as such if we want a return greater than the tangency portfolio we will have to invest 0 in the risk free asset and in fact follow along the efficient frontier of the bullet.
Implications of the one fund theorem = the one fund theorem no longer holds above Mu T
What do we mean when we say risk free borrowing exists at a higher rate than the risk free lending rate?
Risk free borrowing at higher rate = It is possible to lend (invest positively) at the lower rate as we normally would until we hit the tangency portfolio. here it is possible to invest fully in the tangency portfolio or achieve a slightly higher return (same variance) portfolio by borrowing (investing negatively) at the higher borrowing rate. Obviously if we could simply continue borrowing at the lower rate then this would achieve the highest return portfolio
In our course we use excel to solve when No short selling is applied as a restraint. As such we only need to know a few smaller questions concerning this part of the topic.
- What does this mean for our weights?
- What does the MVS where no short selling is allowed look like?
Weights = all weights must be greater than or equal to 1
MVS = a curved bullet that cannot exceed the returns of the highest performing asset nor underexceed the returns from the lowest performing asset. This bullet also stays inside the MVS (risky asset only) bullet and can touch it, but never go out of it).
In the equilibrium model what two conditions hold?
- All investors preferences are satisfied and they hold an optimal portfolio based on their risk preferences
- Markets clear i.e. for every buyer of an asset there is a seller
What does the capital market line determine?
Which equation defines the CML?
What does the security market line determine?
Which equation defines the SML?
CML = determines the expected return of efficient assets (with respect to the total risk) Equation = same equation as we use for the MVS with a risk free asset, however we swap Mu T and Sigma T for Mu M and Sigma M
SML = determines the expected return of all assets (with respect to the systematic risk) Equation = the CAPM equation (where we replace the gradient of a straight line with Beta)
Under the CML what happens to the market portfolio when:
Investors are more risk-averse
Investors are less risk-averse
More = they will not place much money into the market portfolio (preferring the Rf), and it will have a high expected return
Less = they will put more money into the market portfolio and it will have a low expected return
Under the CAPM Assumption 1 states that investors choose between portfolios on the basis of only two things? What are they?
Which 2 conditions justify this assumption?
They are = expected return and standard deviation of returns
1: Asset returns are jointly normally distributed
2: utility functions are quadratic
What is an Isobeta line? What does it help us to understand?
Isobeta line = a line extending horizontally from the CML. This line measures the total risk of an asset (systematic + unsystematic). As we start on the line we have only systematic risk. As we extend through to the right hand side of the line we add more and more unsystematic risk, thus increasing our total risk. However all assets along the line will in fact have the same return.
The line is a good means for understanding that there is no risk premium for unsystematic risk
Why do we use factor models?
What are risk factors?
What exactly does the SFM assume?
What do factor models hope to accomplish?
Factor models = reduce the number of parameters to estimate in OMEGA and can increase the reliability of the estimate
Risk factors = sources of randomness = market index, GDP, employment rate, interest rate, etc.
The SFM = assumes that the randomness of every asset in the market is generated by a single common factor - typically the market portfolio
Accomplish = explain the covariances between the returns of any pair of assets by focusing on one or more factors which affect the assets
What are the three assumptions of the SFM?
What are the implications of assumption 3?
Assumption 1: Expected value of error term is 0
Assumption 2: covariance between the error term and the market return is 0
Assumption 3: covariance between the error term of one asset and the error term of another asset is 0
Implications of assumption 3 = the two assets in question must hence be related only through one factor, the return on the market portfolio
What is a characteristic line?
Characteristic line = straight line plotted in stock returns - market returns space. The line is in fact a regression which achieves a line of best fit between an individual stocks returns and the corresponding market returns.
Equation = ri = ai + Brm
Under the SFM we use our asset weights to determine the portfolio return etc. However what is unique about the situation where we use asset weights to determine our sigma^2epsilon?
Answer = we square our weights.
How do we calcuate R^2?
What does R^2 = 1 imply?
If we have a portfolio of N assets and we continue to add assets until we reach infinity, what will happen to our unsystematic risk?
Calculate R^2 = This is super easy… in fact R^2 simply measures the systematic risk over total risk… Hence we would calculate systematic risk using our equations and then place it over the total risk to produce our R^2 value.
R^2 = 1 implies that our portfolio is fully diversified and includes only systematic risk.
Add assets = Our systematic risk will reach zero as we add more assets and hence diversify our portfolio
How does assumption 2 vary between a single factor model and a multi factor model?
Assumption 2 = Assumption 2 extends from simply being “the covariance between the error term and the single factor is 0” to “ the covariance between the error term and all factors is 0”
Note: The other two assumptions remain the same.
Define arbitrage?
What are the two fundamental assumptions of the APT?
Arbitrage = when there exists a zero-cost portfolio (or security) that yields a non-negative payoff for sure, and with the possibility of yielding a strictly positive payoff
1: Arbitrage opportunities do not exist in the market
2: Security returns are generated by a factor model
What are the two advantages of APT over the CAPM?
1: Less restrictive = APT does not assume that all investors have homogeneous beliefs on which they act optimally (instead APT assumes that investors will exploit arbitrage opportunities so that mispriced assets are driven towards their equilibrium price)
2: Proponents of APT argue that the model can be verified empirically