Updated for the 2026-2027 CFA® Level I curriculum.
A price multiple compares a stock's market price to a fundamental measure like earnings, book value, or sales. CFA Level I tests whether you understand why analysts use these multiples and how they connect back to valuation theory, not just how to calculate one.
After this note, you should be able to explain the rationale for price multiples, link the P/E ratio to its fundamental drivers, and explain why two companies can justifiably trade at different multiples.
Quick Answer
Price multiples like P/E link a stock's market price to a fundamental value driver such as earnings or book value. Analysts use them because they are quick, intuitive, and grounded in valuation theory. The P/E ratio connects directly to the Gordon growth model through the payout ratio, required return, and growth rate. The same logic produces the justified price to book ratio, which explains why similar companies can trade at different multiples for sound fundamental reasons.
Key Takeaways About Price Multiples and Fundamental Drivers
Price multiples compare market price to a fundamental measure: earnings, book value, sales, or cash flow.
Analysts use multiples because they are fast to calculate, easy to compare across companies, and tied to valuation theory.
The justified forward P/E derived from the Gordon growth model is .
A higher payout ratio, lower required return, or higher growth rate raises the justified P/E, holding other factors constant.
A justified multiple is the P/E or P/B value that fundamentals support. It differs from the multiple observed in the market.
Two companies with identical observed P/E ratios can have very different growth and risk profiles.
Differences in ROE, growth, and required return explain why justified price to book ratios vary across firms, even within the same industry.
What You Need to Know for CFA Level I
Explain why analysts rely on price multiples instead of only absolute valuation models.
Derive the relationship between P/E and Gordon growth model inputs: payout ratio, required return, and growth.
Identify how growth, risk, and payout affect the justified P/E and justified P/B.
Recognize that an observed multiple signals over- or undervaluation only after comparing it to a justified multiple.
Apply fundamental reasoning to explain why two similar firms trade at different multiples.
Rationale for Using Price Multiples
Price multiples are popular for practical reasons. They are simple to calculate from public data. They allow quick comparison across companies, sectors, and time periods. They do not require the analyst to forecast a full stream of future cash flows or dividends, which absolute valuation models like the dividend discount model do require.
Multiples also reflect current market sentiment. This makes them useful for gauging how the market is pricing growth and risk, even when that pricing does not match fundamentals. For CFA Level I, the key point is that price multiples are not a shortcut around valuation theory. They are grounded in the same models used for absolute valuation. The P/E ratio, for example, can be derived directly from the Gordon growth model.
How P/E Relates to Fundamentals
Start with the Gordon growth model:
equals expected earnings multiplied by the dividend payout ratio. Substituting and dividing both sides by gives the justified forward P/E:
Where:
= Current stock price
= Expected earnings per share, next period
Payout ratio = Dividends per share divided by earnings per share
= Required return on equity
= Expected constant growth rate of dividends
Three fundamental drivers determine the justified P/E:
Payout ratio. A higher payout ratio raises the justified P/E, holding r and g constant.
Required return (r). A higher required return lowers the justified P/E, because the denominator () increases.
Growth rate (g). A higher growth rate raises the justified P/E, because the denominator shrinks.
These drivers are not fully independent. A company that raises its payout ratio retains less earnings for reinvestment. Lower retention can reduce future growth, which works against the payout effect. Candidates who treat payout ratio and growth as unrelated inputs often reach the wrong directional conclusion.
Why a Multiple Must Be Interpreted in Context
An observed P/E or P/B tells you what the market is currently paying. It does not by itself tell you whether the stock is cheap or expensive. That judgment requires a benchmark, usually the justified multiple implied by fundamentals or the multiple of a comparable company with similar risk and growth.
A high P/E can mean the stock is overvalued. It can also mean the market correctly expects high future growth. A low P/E can mean the stock is undervalued. It can also mean the company carries higher risk or has weaker growth prospects. The multiple alone does not distinguish between these explanations.
Context also includes industry norms, where the company sits in its business cycle, differences in capital structure, and differences in accounting policy that affect reported earnings or book value. Comparing multiples across companies without adjusting for these factors leads to flawed conclusions.
How Fundamental Drivers Can Justify Differences in Observed Multiples
The same logic used to derive justified P/E applies to other multiples. The justified price to book ratio comes from the same Gordon growth framework:
Where:
= Current stock price
= Current book value per share
ROE = Return on equity
= Required return on equity
= Expected constant growth rate
A company with a higher spread between ROE and its required return deserves a higher justified P/B. This explains a common exam scenario: two companies in the same industry can have different observed P/B ratios for a fundamentally sound reason.
The company with higher ROE relative to r, or higher expected growth, supports a higher multiple. The difference is not automatically a mispricing signal.
Worked Example
Two companies in the same industry, Company A and Company B, have the following fundamentals.
Input | Company A | Company B |
|---|---|---|
ROE | 15% | 12% |
Required return () | 10% | 10% |
Growth rate () | 5% | 5% |
Observed market P/B | 2.2 | 1.3 |
Step 1: Calculate the justified P/B for each company
Step 2: Compare observed P/B to justified P/B
Company A trades at 2.2 against a justified P/B of 2.0. Company B trades at 1.3 against a justified P/B of 1.4.
Company A's market price is modestly above what its ROE, growth, and required return support. Company B's market price is modestly below what its fundamentals support. The difference in observed multiples between A and B is largely explained by their different ROE levels, not by market mispricing alone.
Common Exam Traps
Confusing observed multiple with justified multiple
A high P/E is not automatically a sign of overvaluation. Compare it to a justified multiple or a peer with similar risk and growth before drawing a conclusion.
Treating payout ratio and growth as unrelated
Raising the payout ratio reduces retained earnings available for reinvestment, which can lower future growth. Exam questions test whether you catch this offsetting effect.
Applying one industry's typical multiple to another industry
Different industries carry different risk and growth profiles, so their justified multiples differ. A "normal" P/E in one sector can be inappropriate in another.
Giving a valuation conclusion without fundamental reasoning
Stating that a stock is cheap or expensive based on the multiple alone, without referencing ROE, growth, or required return, misses the analytical point of the LOS.
Practice Question
An analyst evaluates a stable, mature company with ROE of 18%, a required return on equity of 12%, and expected growth of 6%. Book value per share is $20. The stock currently trades at $34. Based on the justified price to book ratio, the stock is best described as:
Undervalued, because the market P/B is below the justified P/B.
Overvalued, because the market P/B is above the justified P/B.
Fairly valued, because the market P/B equals the justified P/B.
Correct Answer: A
Reasoning:
The market P/B of 1.7 is below the justified P/B of 2.0. This means the stock trades at a lower multiple than its fundamentals support, indicating undervaluation.
Option B. This reverses the comparison. The market P/B is below, not above, the justified P/B.
Option C. The two values are not equal. 1.7 does not equal 2.0.
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FAQs About Price Multiples and Fundamental Drivers
What is the difference between an observed P/E and a justified P/E?
The observed P/E is what the market currently pays for a stock's earnings. The justified P/E is what fundamentals such as payout ratio, required return, and growth support. Comparing the two shows whether a stock looks over- or undervalued relative to its own fundamentals.
Why do similar companies trade at different P/B ratios?
Differences in ROE, growth, and required return change the justified P/B for each company. A company with a higher ROE relative to its required return supports a higher P/B, even within the same industry.
Does a high P/E always mean a stock is overvalued?
No. A high P/E can reflect strong expected growth rather than overvaluation. The multiple needs to be compared against a justified multiple or a peer with similar fundamentals before drawing that conclusion.