A Stock Has A Beta Of 2.57 And An Expected Return Of 28.0%. The T-bill Rate Is 7.6%. Calculate The Portfolio
Understanding how to calculate the expected return of a portfolio is a fundamental aspect of investment analysis, especially for investors aiming to optimize their asset allocation. When given specific data points such as a stock’s beta, its expected return, and the risk-free rate (represented here by T-bills), investors can utilize various financial models to determine the appropriate portfolio composition. This article provides a comprehensive guide to calculating the expected return of a portfolio, emphasizing the importance of beta and risk premiums in such calculations.
Understanding Key Financial Concepts
Before diving into calculations, it’s crucial to understand the core concepts involved in portfolio expected return estimation.
Beta: A Measure of Systematic Risk
Beta (β) quantifies a stock's sensitivity to market movements. A beta of 1 indicates that the stock’s price moves in line with the overall market. A beta greater than 1 suggests higher volatility than the market, whereas less than 1 indicates lower volatility.- Beta of 2.57 signifies that the stock is significantly more volatile than the average market, implying that it tends to amplify market movements.
Expected Return and the Capital Asset Pricing Model (CAPM)
The CAPM provides a theoretical framework to determine the expected return of an asset based on its systematic risk:\[
E(Ri) = Rf + \betai \times (E(Rm) - R_f)
\]
Where:
- \( E(R_i) \) = Expected return of the asset
- \( R_f \) = Risk-free rate (T-bill rate)
- \( \beta_i \) = Beta of the asset
- \( E(R_m) \) = Expected return of the market
This model emphasizes the relationship between risk and return, implying that higher risk (beta) should be compensated with higher expected returns.
Calculating the Expected Return of the Stock
Given data:
- Beta (\( \beta \)) = 2.57
- Expected return of the stock (\( E(R_i) \)) = 28.0%
- T-bill rate (\( R_f \)) = 7.6%
The goal is to find the expected market return (\( E(R_m) \)) based on the provided data or to understand how the stock’s return relates to market expectations.
Using the CAPM formula rearranged:
\[
E(Ri) = Rf + \betai \times (E(Rm) - R_f)
\]
Plugging in the known values:
\[
28.0\% = 7.6\% + 2.57 \times (E(R_m) - 7.6\%)
\]
To find \( E(R_m) \):
\[
28.0\% - 7.6\% = 2.57 \times (E(R_m) - 7.6\%)
\]
\[
20.4\% = 2.57 \times (E(R_m) - 7.6\%)
\]
\[
E(R_m) - 7.6\% = \frac{20.4\%}{2.57}
\]
\[
E(R_m) - 7.6\% \approx 7.93\%
\]
\[
E(R_m) \approx 7.6\% + 7.93\% = 15.53\%
\]
Interpretation:
- The expected market return based on this stock’s parameters is approximately 15.53%.
- The high beta indicates high systematic risk, which is compensated with a high expected return of 28%.
Constructing the Portfolio: Determining Asset Weights
To calculate the overall expected return of a portfolio, we need to determine the weights of individual assets within it. Typically, investors aim to balance risk and return by adjusting these weights.
Suppose the investor is considering a portfolio composed of:
- The high-beta stock (with beta = 2.57)
- A risk-free asset (T-bills at 7.6%)
The key question: What proportion of the portfolio should be invested in the stock versus the risk-free asset to achieve a desired return or risk profile?
Using the Capital Market Line (CML)
The CML demonstrates the risk-return trade-off of efficient portfolios combining the risk-free asset and the market portfolio. The formula for the expected return of a portfolio combining these two assets is:\[
E(Rp) = Rf + \frac{\sigmap}{\sigmam} \times (E(Rm) - Rf)
\]
Where:
- \( E(R_p) \) = Expected return of the portfolio
- \( R_f \) = Risk-free rate
- \( \sigma_p \) = Portfolio standard deviation
- \( \sigma_m \) = Market standard deviation
Note: Since the specific standard deviations are not provided here, a more straightforward approach involves the concept of leveraging or deleveraging the portfolio based on beta.
Calculating Portfolio Beta and Expected Return
The beta of the portfolio (\( \beta_p \)) is the weighted sum of individual asset betas:\[
\betap = ws \times \betas + wf \times \beta_f
\]
Where:
- \( w_s \) = weight of the stock in the portfolio
- \( \beta_s = 2.57 \)
- \( w_f \) = weight of the risk-free asset (T-bills)
- \( \beta_f = 0 \) (since risk-free assets have zero beta)
The sum of weights:
\[
ws + wf = 1
\]
The expected return of the portfolio:
\[
E(Rp) = ws \times E(Rs) + wf \times R_f
\]
Given that:
- \( E(R_s) = 28.0\% \)
- \( R_f = 7.6\% \)
Suppose the investor aims to achieve a specific portfolio expected return—for example, matching the stock’s expected return (28%) or a lower/higher target.
---
Example: Constructing a Portfolio with a Desired Expected Return
Scenario 1: Portfolio expected return is 20%
Using:
\[
E(Rp) = ws \times 28.0\% + (1 - w_s) \times 7.6\%
\]
Set:
\[
20\% = ws \times 28\% + (1 - ws) \times 7.6\%
\]
Solve for \( w_s \):
\[
20\% = 28\% \times ws + 7.6\% - 7.6\% \times ws
\]
\[
20\% - 7.6\% = w_s \times (28\% - 7.6\%)
\]
\[
12.4\% = w_s \times 20.4\%
\]
\[
w_s = \frac{12.4\%}{20.4\%} \approx 0.608
\]
Interpretation:
- Invest approximately 60.8% of the portfolio in the stock.
- Remaining 39.2% in T-bills.
Portfolio beta:
\[
\beta_p = 0.608 \times 2.57 + 0.392 \times 0 = 1.565
\]
This portfolio has a beta of approximately 1.565, indicating it is more volatile than the market.
---
Example: Targeting the Market Portfolio
If an investor wishes to construct a portfolio with a beta equal to the market (i.e., beta = 1), they can solve:
\[
\betap = ws \times 2.57 + (1 - w_s) \times 0 = 1
\]
\[
w_s \times 2.57 = 1
\]
\[
w_s = \frac{1}{2.57} \approx 0.389
\]
Portfolio composition:
- About 38.9% in the stock.
- About 61.1% in T-bills.
Expected return:
\[
E(R_p) = 0.389 \times 28\% + 0.611 \times 7.6\% \approx 10.89\% + 4.65\% = 15.54\%
\]
This aligns with the previously calculated expected market return, confirming the consistency of the model.
---
Implications for Investors
Understanding the relationship between beta, expected return, and asset allocation empowers investors to make informed decisions. Here are some key takeaways:
- High-beta stocks like the one discussed (beta = 2.57) offer the potential for higher returns but come with increased risk.
- Risk-free assets such as T-bills provide stability but lower returns.
- Portfolio construction involves balancing these assets to match the investor’s risk appetite and return objectives.
Risk-Return Tradeoff
Investors seeking higher returns must accept higher systematic risk, often achieved through leveraged positions in high-beta stocks. Conversely,