1.3: Portfolio & CAPM Theory Flashcards
What does portfolio theory assume?
That investors only care about the overall mean and variance of their portfolios
- mean is good
- variance is bad
What is an efficient portfolio?
A portfolio that only contains systematic risk, and hence cannot be diversified further. No other portfolio offers a higher expected return with lower volatility
What is a natural candidate for an efficient portfolio?
The market portfolio; a portfolio of all stocks and securities traded in the capital market. Common practice is to use the S&P 500 as an approximation.
How can be measure the systematic risk of a security?
By calculating the sensitivity of the security’s return to the return of the market portfolio, which is the beta of the security
What is the beta of a security?
The expected percentage change in its return given a 1% change in the return of the market portfolio
What is the average of beta of a stock in the market?
About 1:
- cyclical industries have revenues that vary greatly over the business cycle and hence betas over 1
- non-cyclical firms tend to have betas less than 1
What is the market risk premium?
The difference between the market portfolio’s expected return and the risk-free interest rate. It reflects investors’ risk tolerance and determines the market price of risk in the economy. The reward investors expect to earn for holding a portfolio with a beta of 1 (the market portfolio)
What is the equation for estimating the cost of capital often referred to as?
The Capital Asset Pricing Model (CAPM).
What is an inefficient portfolio?
A portfolio where it is possible to find another portfolio that is better in terms of both expected return and volatility
What effect does correlation have on the expected return and volatility of a portfolio?
- No effect on expected return
- The lower the correlation, the lower the volatility we can obtain. The curve showing the portfolios will bend to the left to a greater degree.
What are the benefits of diversification when stocks are perfectly correlated?
No benefits.
What is a short sale/short position?
Investing a negative amount in a stock. You sell a stock today that you do not own, with the obligation to buy it back in the future (negative weight in portfolio)
When is short selling profitable?
When the stock’s price declines in the future
What is the efficient frontier?
The curve that connects the efficient portfolios
What is an alternative way to reduce risk, besides diversification?
Keeping some of our money in a safe, no-risk investment like treasury bills (but it will reduce expected return)
What can aggressive investors do if they want to be able to invest more in the stock market?
Borrow money
What is the volatility and covariance of a risk-free asset with a portfolio?
Both are zero, since the risk-free rate is fixed and does not move with the portfolio
What is a levered portfolio?
A portfolio that consists of a short position in the risk-free investment
What is the Sharpe ratio?
The slope of a line through a given portfolio P. It measures the ratio of reward-to-volatility provided by a portfolio.