FIN 3400 — Finance for Non-Financial Managers · MDC Kendall · Fall 2026
Module 3 — Exam: Dec 6 (200 pts)
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From Historical to Expected Returns
Chapter 9 taught us to measure historical risk and return. But investors and managers don't invest in the past — they invest in the future. This chapter shifts from looking backward to looking forward.
Why Forward-Looking Estimates Matter
Investors need expected returns to decide whether a stock is worth buying
Managers need to know what return shareholders require — that's the hurdle rate for new projects
Both need to separate the risk that matters (market risk) from the risk that doesn't (firm-specific risk, which diversification eliminates)
The bridge: Last chapter showed that diversification eliminates firm-specific risk. So if you're a diversified investor, you shouldn't be compensated for bearing firm-specific risk — you chose not to diversify! Only market risk earns a risk premium. This insight leads directly to CAPM and beta.
Computing Expected Return
Expected return is the probability-weighted average of all possible returns:
E(R) = Σ [pₛ × Rₛ]
Where pₛ = probability of scenario s, and Rₛ = return in scenario s.
Example
Scenario
Probability
Return
Weighted Return
Boom economy
25%
+25%
6.25%
Normal growth
50%
+10%
5.00%
Recession
25%
−10%
−2.50%
Expected Return
8.75%
Risk of Expected Return
We compute the standard deviation of expected returns the same way as historical returns — measuring how far each scenario's return deviates from the expected return, weighted by probability. This tells us the uncertainty around our 8.75% estimate.
Risk Premiums: The Reward for Risk
Every required return has two components:
Required Return = Risk-Free Rate + Risk Premium
The Components
Risk-free rate — the return on a riskless investment, typically U.S. Treasury securities. It equals the real interest rate plus expected inflation. You get this just for waiting — no risk involved.
Risk premium — the extra return investors demand for bearing risk. This is the reward for uncertainty.
Market Risk Premium
The market risk premium is the return on the overall stock market minus the risk-free rate:
Market Risk Premium = R_market − R_f
Historically (1950–2023), the average market risk premium has been about 8.7% per year. But it varies enormously by decade:
Decade
Risk Premium
1950s
18.8%
1970s
1.2%
1990s
14.1%
2000s
−1.8%
2010s
13.5%
Why this matters: The market risk premium is a key input to CAPM. If you use 8.7% but the true premium is lower (as some academics argue), you'll overvalue stocks and accept too many projects. This single assumption drives trillions of dollars in corporate investment decisions.
The Capital Asset Pricing Model (CAPM)
The Capital Asset Pricing Model is the most famous equation in finance. It specifies the exact relationship between a stock's required return and its market risk:
Required Return = R_f + β × (R_market − R_f)
Breaking It Down
R_f — risk-free rate (the baseline return for zero risk)
β (beta) — the stock's sensitivity to market movements
(R_market − R_f) — the market risk premium (reward for average market risk)
β × (R_market − R_f) — the stock's specific risk premium
The Logic
CAPM says: your required return equals the risk-free rate plus a risk premium proportional to your stock's beta. A stock with beta = 1 has average market risk and earns the market risk premium. A stock with beta = 2 has double the market risk and earns double the premium. A stock with beta = 0.5 has half the market risk and earns half the premium.
Example: Apple
With a risk-free rate of 4%, market return of 10%, and Apple's beta of 1.31:
Why CAPM is powerful: It gives you a single number — the required return — that you can use as a discount rate for valuing stocks, as a hurdle rate for corporate projects, or as a benchmark for evaluating investment performance. It distills the entire risk-return relationship into one elegant equation.
Beta: Measuring Market Risk
Beta measures how much a stock moves with the overall market. It's the sensitivity of a stock's returns to market returns:
Interpreting Beta Values
Beta
Risk Level
What It Means
β = 0
No market risk
Stock doesn't move with market at all (theoretical)
β = 0.5
Low risk
Stock moves half as much as the market
β = 1.0
Average risk
Stock moves in sync with the market
β = 1.5
High risk
Stock moves 50% more than the market
β = 2.0
Very high risk
Stock moves double the market
β < 0
Negative
Stock moves opposite to market (rare)
Beta values for selected Dow Jones Industrial Average stocks
Portfolio Beta
A portfolio's beta is simply the weighted average of its stocks' betas:
β_portfolio = Σ (wₖ × βₖ)
This makes it easy to see how adding a stock changes your portfolio's market risk. Adding a high-beta stock (like Boeing at 1.56) increases portfolio risk; adding a low-beta stock (like Verizon at 0.40) decreases it.
Where to find beta: You can compute it yourself from historical returns (regression analysis), or look it up on Yahoo Finance, MarketWatch, or MSN Money. Different sources may show slightly different betas because they use different time periods and return intervals — beta is an estimate, not a constant.
The Security Market Line
The Security Market Line (SML) is the graphical representation of CAPM. It plots required return (y-axis) against beta (x-axis):
The intercept is the risk-free rate (R_f) — the return when beta = 0
The slope is the market risk premium (R_market − R_f)
Every stock should plot on this line if CAPM holds
Using the SML
Stocks above the SML are undervalued — they offer more return than their risk justifies (buy!). Stocks below the SML are overvalued — they offer less return than their risk requires (sell!).
SML vs. CML: The Capital Market Line (CML) uses standard deviation as the risk measure and applies only to efficient portfolios. The SML uses beta as the risk measure and applies to any stock or portfolio — efficient or not. The SML is the more general and useful tool for individual securities.
Concerns About Beta
Different time periods and return intervals yield different betas
Beta depends on the firm's future plans, not just its past
Empirically, beta doesn't predict future returns as well as theory suggests
This has led some practitioners to use alternative models (like the constant-growth model for required return)
Market Efficiency: Can You Beat the Market?
The Efficient Market Hypothesis (EMH) argues that stock prices already reflect all available information. If true, you can't consistently beat the market — because any edge you find is already priced in.
Three Forms of Efficiency
Weak Form
Prices reflect all past trading data
Price and volume charts are already in the price
Technical analysis would be useless
Semi-Strong Form
Prices reflect all public information
Financial statements, news, analyst reports
Fundamental analysis would be useless
Strong Form
Prices reflect ALL information — public and private
Even insider information is already in the price
This is unlikely to be fully true, but the market is probably at least semi-strong form efficient
Implications: If markets are semi-strong efficient, active stock picking is a losing game for most investors. This is why index funds and ETFs have grown so popular — if you can't beat the market, join it at minimal cost. Warren Buffett's famous bet: he wagered $1M that an S&P 500 index fund would outperform hedge funds over 10 years. He won.
Behavioral Finance: Humans Aren't Rational
EMH assumes investors are perfectly rational. Behavioral finance studies the cognitive biases that make real investors act irrationally:
Common Biases
Overconfidence — people overestimate their knowledge and underestimate risks. 80% of drivers think they're above average — the same applies to investors.
Loss aversion — losses hurt about twice as much as equivalent gains feel good. This makes investors hold losers too long and sell winners too early.
Herding — people follow the crowd, creating bubbles and crashes. The dot-com bubble (2000) and crypto mania (2021) are classic examples.
Fear and panic — in March 2020, the S&P 500 fell 34% in 33 days, driven by pandemic fear. It then recovered to new highs within months.
The tension: Behavioral finance doesn't disprove EMH — it explains why markets can be inefficient in the short run even if they're efficient in the long run. Overconfidence creates mispricing; arbitrageurs correct it. The question is how fast the correction happens, and whether you can exploit it before it's gone.
Required Return from the Constant-Growth Model
Because beta has empirical limitations, some practitioners use an alternative: the constant-growth model to infer required return. If a stock is efficiently priced, we can rearrange the Gordon Growth formula:
i = (D₁ / P₀) + g
The required return equals the dividend yield plus the growth rate. This uses current market data (price and dividend) rather than historical beta regressions.
When to Use Each Method
Method
Best When
Weakness
CAPM
Sufficient historical data; stable business
Beta may not predict future risk
Constant-Growth
Stock pays steady, growing dividends
Doesn't work for irregular or no dividends
For managers: Understanding required return is essential. If your shareholders require 12% and your new project earns only 10%, you're destroying value — even though the project is "profitable." The bar isn't zero; it's the shareholders' required return. Every project must clear that hurdle to create value.
Key Takeaways
Expected return = probability-weighted average of possible returns
Beta measures market risk — β > 1 means riskier than market, β < 1 means safer
Portfolio beta = weighted average of individual stock betas
The Security Market Line graphs CAPM — stocks above it are undervalued
EMH: markets may reflect all public information (semi-strong form likely true)
Behavioral finance explains short-term irrationality within an otherwise efficient market
Constant-growth model offers an alternative to CAPM: i = (D₁/P₀) + g
Managers must earn at least the required return to create shareholder value
Next up: Chapter 11 — Calculating the Cost of Capital. We'll combine everything: the cost of debt (Chapter 7), cost of equity (CAPM from this chapter), and capital structure weights into the Weighted Average Cost of Capital (WACC) — the master hurdle rate for corporate finance.
Further Learning Resources
Explore these to deepen your understanding of this chapter's topics: