The Capital Asset Pricing Model (CAPM) is one of the most-tested formulas in the CII R02 exam — and one of the most misunderstood. The good news: the equation itself is simple once you know what each letter actually means.
The CAPM equation
E(Rᵢ) = R_f + βᵢ × (R_m − R_f)
In plain English:
Expected return = risk-free rate + beta × equity risk premium
| Symbol | Meaning |
|---|---|
| E(Rᵢ) | Expected return on the investment (what we're solving for) |
| R_f | Risk-free rate (usually a 10-year UK gilt yield) |
| β | Beta — how sensitive the share is to the market (1.0 = moves with market) |
| R_m | Expected return on the whole market |
| (R_m − R_f) | Equity risk premium — extra return for taking on equity risk |
Worked example
Assume:
- Risk-free rate (R_f) = 4%
- Expected market return (R_m) = 9%
- Beta of Share A = 1.4
Step 1 — Equity risk premium: 9% − 4% = 5%. Step 2 — Multiply by beta: 1.4 × 5% = 7%. Step 3 — Add the risk-free rate: 4% + 7% = 11%.
Expected return on Share A = 11%.
A share with beta of 0.6 in the same market would only need: 4% + (0.6 × 5%) = 7%.
What R02 actually tests
The exam rarely asks you to recite the formula in the abstract — instead it gives you three numbers and asks you to compute the fourth. Common variants:
- Solve for E(Rᵢ) — the standard "what should this share return?" question
- Solve for beta — given expected return, R_f, and R_m, rearrange the formula
- Compare two shares — pick the one whose actual return exceeds CAPM's expected return (it's "underpriced")
How to remember it
Think of CAPM as a two-part fee for owning a share:
- The minimum payment for parking your money anywhere (R_f)
- A bonus for accepting market risk (the equity risk premium), scaled by how risky this particular share is (β)
That's it. Anything called "expected return on equity" in R02 is almost certainly a CAPM question dressed up.
Common R02 traps
- Confusing R_m with the equity risk premium. R_m is the total market return; the premium is R_m − R_f.
- Forgetting to multiply by beta. A naked addition of R_f + (R_m − R_f) gives you the market return, not the share's return.
- Using a negative beta wrong. Negative-beta shares (rare — typically gold miners) reduce expected return below the risk-free rate.
- Mixing up arithmetic and percentages. Keep everything in the same units (decimals or percentages, not both).
Where CAPM fits in R02
CAPM sits in the portfolio theory section alongside:
- Modern Portfolio Theory (Markowitz)
- The efficient frontier
- The Sharpe ratio (CAPM's close cousin — uses the same R_f and excess return idea)
If you can confidently produce a CAPM answer in under 60 seconds, you've banked some of the easiest marks in R02.