Efficient Market Hypothesis
Also written EMH · Efficient Market Hypothesis (EMH)
The proposition that share prices already incorporate and reflect all relevant information — which, if true, leaves nothing for an analyst to find by studying that information.
In plain language
If every fact about a company is already in its price, then the price is the answer and there is no gap between price and value to exploit. That is the Efficient Market Hypothesis, and it is the idea against which the entire research analyst profession defines itself.
The workbook does not endorse it. It introduces EMH precisely to say that fundamental analysis contradicts it: profits come from identifying a good investment and buying it at the right price, which presupposes that the price is sometimes wrong.
How it works
The workbook states EMH twice, in two chapters, and the two statements point in opposite directions.
In Chapter 4.4, having explained that an investor should buy below intrinsic value and sell above it, it says this thought process is in contradiction of the Efficient Market Hypothesis, which propagates that share prices incorporate and reflect all relevant information.
In Chapter 15.3.1, setting out the first tenet of Dow Theory — the market discounts everything — it says that tenet aligns with the Efficient Market Hypothesis and is foundational to technical analysis, which assumes price action reflects all relevant data.
So the same hypothesis is presented as the enemy of fundamental analysis and the friend of technical analysis. Read strictly, that cannot hold: a market that has already absorbed all relevant information has absorbed the information contained in past prices too, which would leave the chartist no better placed than the fundamental analyst. The workbook's third position, in Chapter 4.6, is the behavioural one — that prices move away from fair value, up and down, because of the fear and greed of market participants.
Answer whichever chapter the question comes from.
A worked example
Put the hypothesis to work on a decision an Indian investor actually faces.
A large-cap active fund charges a total expense ratio of 1.8%. An index fund tracking the same benchmark charges 0.20%. The benchmark itself returns 12% a year before costs.
If EMH holds, the active manager cannot systematically find mispricing, so gross alpha is zero and each investor simply receives the benchmark less costs:
Active fund net return = 12.0 − 1.8 = 10.2%
Index fund net return = 12.0 − 0.2 = 11.8%
On Rs 10 lakh invested for 15 years:
Active : 10,00,000 × 1.102^15 = Rs 42.92 lakh
Index : 10,00,000 × 1.118^15 = Rs 53.27 lakh
Gap = Rs 10.35 lakh
The gap is larger than the original investment. That Rs 10.35 lakh is the hurdle the active manager must clear before the investor is a rupee better off — which is the practical content of the hypothesis, and also why the workbook sets active and passive investing out as a genuine choice in Chapter 4.1 rather than declaring a winner.
Why NISM asks about it
Chapter 4 (section 4.4) introduces EMH as the proposition fundamental analysis contradicts, and Chapter 15 (section 15.3.1) links it to the first tenet of Dow Theory. Expect a definitional question — prices incorporate and reflect all relevant information — and a question on the relationship between EMH and fundamental analysis, where the workbook's answer is contradiction.
Common exam traps
- The workbook takes both positions. Chapter 4.4: fundamental analysis contradicts EMH. Chapter 15.3.1: the "market discounts everything" tenet aligns with EMH and is foundational to technical analysis. Quote the chapter the question is drawn from.
- EMH says information is in the price, not that the price is right. It is not a claim that markets never fall or that valuations are always sensible.
- Chapter 4.6 sets out the opposite view, that prices leave fair value because of fear and greed. The workbook does not resolve the conflict, and neither should an exam answer.
- EMH is not an argument that research is pointless. Chapter 4.2 spends its length on how much work getting good information takes — which is what an efficient market would have to have already absorbed.
- Mosaic analysis is the analyst's legitimate response (Chapter 4.2.1): assembling individually insignificant public and non-public pieces into an insight. Acting on a single piece of unpublished price sensitive information is not.
- Do not read EMH as a recommendation of passive investing. Chapter 4.1 presents active and passive as two approaches with different objectives, not a verdict.
Check yourself
1.The fundamental analyst's thought process — that price can diverge significantly from fair value, creating a profit-making opportunity — is described in the workbook as:
- a)A direct application of the Efficient Market Hypothesis
- b)In contradiction of the Efficient Market Hypothesis
- c)Unrelated to the Efficient Market Hypothesis
- d)A special case of the Efficient Market Hypothesis that applies only to small-cap stocks
Show the answer
Answer: (b) In contradiction of the Efficient Market Hypothesis
The workbook says this thought process is in contradiction of Efficient Market Hypothesis (EMH), which propagates that share prices incorporate and reflect all relevant information.
The logic is worth holding on to. If EMH were fully true, price would always equal fair value, there would be no divergence to exploit, and estimating intrinsic value would be pointless. Fundamental analysis only earns its keep because prices can be wrong.
Option A inverts the relationship. Option C is wrong because the workbook explicitly links them. Option D invents a size-based carve-out found nowhere in the text.
Where this is taught
- Series XXI-B · Chapter 13: Concept of informational Efficiencyintroduced here
- Series XV · Chapter 4: Fundamentals of Researchintroduced here
Related terms
- Dow TheoryCharles Dow's six-tenet framework: the market discounts everything, moves in primary, secondary and tertiary trends, must be confirmed by indices and volume, and trends persist until clearly reversed.
- Fundamental analysisEstimating what a share is worth from the profits and cash flows the business will generate, then buying only when the market price sits below that estimate.
- Intrinsic valueWhat an asset is actually worth — the present value of the cash it will generate over its remaining life, as against whatever price the market is quoting today.
- Margin of safetyThe gap between a security's estimated intrinsic value and the lower price paid for it — the cushion that protects the buyer when the estimate turns out to be wrong.
- Technical analysisForecasting price direction from past price and volume alone, on the assumption that everything worth knowing about a company is already in its price.
- Unpublished price sensitive informationInformation about a company or its securities that is not generally available and that would, on becoming available, be likely to materially affect the price of the security.
- Weak-form EfficiencyThe hypothesis that current prices already reflect all historical market information — past prices, returns and volumes — so technical analysis cannot earn above-average risk-adjusted returns.
- Semi-strong-form EfficiencyThe hypothesis that prices reflect all historical and publicly available information and adjust rapidly to news — so neither technical nor fundamental analysis earns above-average risk-adjusted returns.
- Strong-form EfficiencyThe most extreme form of the efficient market hypothesis: prices reflect all historical, public and insider information, so no group of investors can earn above-average risk-adjusted returns.
- Market anomalyA pattern of returns that departs from what an asset's fundamentals and risk — as measured by CAPM or another pricing model — say it should earn, and so contradicts market efficiency.
- Behavioural financeThe study of how psychology shapes the decisions of market participants, individually and in groups, and how those decisions show up as gaps and anomalies in financial markets.
- Informational EfficiencyHow fully and quickly security prices reflect available information. It is what "market efficiency" usually means, as against operational efficiency, which is about transaction costs.
- Random Walk HypothesisThe early form of the efficient market model: security price changes occur randomly, so successive one-period returns are independent and identically distributed.
- Size AnomalyThe finding that small firms, measured by total market value, have consistently earned larger risk-adjusted returns than large firms — contradicting market efficiency.
- January effectA market anomaly in the US: year-end tax selling pushes prices down in late November and December, and the buying back in early January pushes them up — a pattern inconsistent with market efficiency.
- Internal contradiction of efficiencyThe paradox that a market can only become informationally efficient if enough participants believe it is not — because it is their search for mispricing that drives prices to fair value.
- Active investingAn investing approach that involves picking individual securities to try to beat the return of the broader asset class, rather than simply tracking it.
- Passive investingAn approach that buys a broad basket of securities, typically by tracking an index, to earn the return of the asset class as a whole rather than trying to beat it.
- Unbiased EstimateThe technical definition of an efficient market price: the market price is an unbiased estimate of a security's true value, so deviations are random rather than one-sided.