Beta
Also written β · Beta coefficient
How sharply a share moves relative to the market index — beta 1 moves with the index, above 1 amplifies it, below 1 dampens it. The standard measure of systematic risk.
In plain language
Beta answers one question: when the index moves, how much does this share move?
A beta of 1 means it tracks the index. A beta of 1.5 means it tends to move half again as hard in both directions — up 15% when the Nifty rises 10%, down 15% when it falls 10%. A beta of 0.6 means it moves less than the index either way.
It measures only the risk that comes from being in the market at all. The risk of a factory fire or a failed product is specific to the company and does not show up in beta, because an investor can diversify it away.
How it works
Beta is the slope of a regression of the share's returns against the index's returns, usually over one to five years of data.
The pattern is consistent across sectors: banks, metals, real estate and capital goods carry high betas because they depend on the credit and investment cycle. Consumer staples, pharmaceuticals and utilities carry low betas because people buy soap and medicine in a downturn too.
The formula
β = Covariance (stock return, market return) ÷ Variance (market return)
Expected move in the stock = β × move in the index
A worked example
An investor holds three shares. The Nifty falls 12% in a quarter.
| Holding | Beta | Expected move | Value before | Value after |
|---|---|---|---|---|
| A metals producer | 1.6 | −19.2% | Rs 3,00,000 | Rs 2,42,400 |
| A private bank | 1.2 | −14.4% | Rs 4,00,000 | Rs 3,42,400 |
| An FMCG company | 0.5 | −6.0% | Rs 3,00,000 | Rs 2,82,000 |
| Portfolio | 1.11 | −13.3% | Rs 10,00,000 | Rs 8,66,800 |
The portfolio beta is the value-weighted average of the individual betas: (0.3 × 1.6) + (0.4 × 1.2) + (0.3 × 0.5) = 1.11. The portfolio fell about Rs 1.33 lakh where a pure index holding would have fallen Rs 1.20 lakh — the cost of carrying more systematic risk than the market.
Why NISM asks about it
Chapter 12 (Fundamentals of Risk and Return) defines beta; Chapter 10 uses it inside CAPM to set the cost of equity. Expect straightforward "index up x%, beta y, what happens to the stock" calculations, and portfolio-beta questions using weighted averages.
Common exam traps
- Beta measures systematic risk only. A high-beta share is not "riskier" in every sense — a low-beta company can still go bankrupt from a company-specific failure.
- Portfolio beta is a weighted average of component betas, weighted by value, not an average of the numbers.
- Beta works in both directions. A beta of 1.8 is not a promise of outperformance; in a falling market it is the reason the portfolio falls hardest.
- A negative beta is possible — gold and gold miners sometimes show one. It means the asset tends to rise when the market falls.
- Beta is historical and unstable. It changes as a company's debt and business mix change.
Where this is taught
- Series VIII · Chapter 3: Introduction to Forwards and Futuresintroduced here
- Series XIX-B · Chapter 3: Introduction to Category III AIF Ecosystemintroduced here
- Series XXI-B · Chapter 16: Introduction to Capital Market Theoryintroduced here
- Series XVII · Chapter 5: Evaluating Fund Performance & Fund Selectionintroduced here
- Series XXI-A · Chapter 3: Investing in Stocksintroduced here
- Series XIX-E · Chapter 3: Introduction to Modern Portfolio Theory and Capital Market Theoryintroduced here
- Series XIX-D · Chapter 3: Alternative Investment Funds in India and its Suitabilityintroduced here
- Series V-A · Chapter 10: Risk, Return and Performance of Fundsintroduced here
- Series XIX-A · Chapter 1: Overview of Alternative Investmentsintroduced here
- Series XV · Chapter 10: Valuation Principlesintroduced here
- Series X-A · Chapter 16: Portfolio Performance Measurement and Evaluationintroduced here
- Series V-D · Chapter 10: Risk, Return and Performance of Fundsintroduced here
- Series XIX-C · Chapter 5: Introduction to Capital Market Theoryintroduced here
- Series XXI-B · Chapter 20: Performance Measurement and Evaluation of Portfolio Managers
- Series XIX-E · Chapter 4: Alternative Investment Funds in India and its Suitability
- Series XXI-A · Chapter 10: Performance Measurement and Evaluation of Portfolio Managers
- Series XV · Chapter 12: Fundamentals of Risk and Return
- Series XIX-E · Chapter 10: Investment Strategies
Related terms
- CAPMA model that prices the return an investor should demand from a share: the risk-free rate plus beta times the market risk premium.
- Sharpe ratioReturn earned above the risk-free rate divided by standard deviation — how much reward an investment produced for each unit of total risk its holder had to live with.
- Standard deviationA measure of how far returns typically stray from their own average — the standard statistic for total risk, counting company-specific and market-wide causes alike.
- Systematic riskThe part of an investment's risk that comes from economy-wide forces moving every asset at once — it cannot be diversified away, and it is the only risk the market pays you to carry.
- AlphaThe return a fund earned above what its beta and the benchmark say it should have earned — the slice of performance left over once the market has been given credit for its share.
- Market-Neutral StrategyA Category III AIF strategy taking equal long and short exposures within a sector, industry or market-cap segment so that portfolio beta is zero or close to zero.
- Directional StrategyA Category III AIF strategy that takes a net long or net short position on stocks or an index, betting on the market's direction; short-bias and dedicated-long are its variants.
- Short-bias StrategyA directional strategy in which the manager holds both long and short positions but keeps a net short exposure to the broad market, so the fund benefits when the market falls.
- VarianceA measure of how widely a scheme's periodic returns fluctuate around its own average return — the square of standard deviation, and a risk measure relevant to both debt and equity schemes.
- Arbitrage Pricing TheoryA multifactor alternative to CAPM, developed by Stephen Ross, in which expected return depends on several risk factors — each with its own beta — instead of the market alone.
- Core and satelliteA portfolio built from a large, low-cost, usually passive core — about 70% to 80% — plus smaller satellite portions managed actively to capture shorter-term opportunities.
- Market ProxyA practical stand-in for the theoretical market portfolio — usually a broad-based equity index. The choice matters: an incorrect proxy distorts beta and the security market line.
- Single-factor modelThe workbook's own term for CAPM: a model that explains an asset's return using just one risk factor, market risk, unlike the several factors used in APT and other multifactor models.
- Undervalued securityUnder CAPM, a security whose estimated return plots above the Security Market Line — earning more than its systematic risk (beta) warrants under market equilibrium.
- Overvalued securityUnder CAPM, a security whose estimated return plots below the Security Market Line — it is expected to earn less than its systematic risk warrants under market equilibrium.
- Regression of beta toward the meanAn empirical finding in the tests of CAPM: high-beta portfolios tend to drift down towards 1.00 over time, and low-beta portfolios tend to drift up towards 1.00.
- Market riskThe risk of loss from movements in market prices — one named category in a manager's risk framework, alongside credit, liquidity and operational risk, and the one measured with VaR and stress tests.
- CovarianceA measure of the degree to which the returns of two assets move together relative to their own averages — the building block of portfolio risk, standardised into the correlation coefficient.
- Market PortfolioThe tangency portfolio M of all risky assets worldwide in market proportions — the one risky portfolio every rational investor holds once a risk-free asset exists; indices serve as its proxy.
- Security Market LineThe graph of CAPM: expected return plotted against beta. In equilibrium every asset lies on it — a security plotting above is undervalued, one plotting below is overvalued.
- CAGRThe single smoothed annual rate at which a starting value would have to grow, compounding each year, to reach the ending value over a given period.
- WACCThe blended after-tax rate a company pays on all its capital, equity and debt weighted by how much of each it uses — and therefore the discount rate for free cash flow to the firm.
- Fund factsheetThe monthly scheme summary an AMC publishes voluntarily — portfolio, performance, risk measures and investment details in one document. It is an AMFI best practice, not a statutory requirement.
- DiversificationSpreading an exposure across holdings that do not move together, so that total risk falls by more than total return does — minimising risk per unit of return.
- Portfolio betaThe weighted average of the betas of the holdings in a portfolio — the measure of its systematic, non-diversifiable risk used in CAPM, the Treynor ratio and market-neutral strategies.
- Beta ManagementThe manager's job of keeping a fund's systematic risk in line with the strategy stated in its private placement memorandum, rather than letting the portfolio beta drift with the market.
- Specific Company Risk PremiumAn extra slice added to the discount rate for one particular company, on top of beta and the market risk premium, to price the unsystematic risk that the CAPM does not capture.
- Unsystematic riskThe part of an investment's risk that belongs to one company or one issuer — a strike, a fraud, a downgrade — and which diversification can remove, unlike market-wide systematic risk.
- Treynor ratioRisk premium per unit of market risk — the return a scheme earned above the risk-free rate, divided by its beta rather than by its standard deviation.
- Defensive stocksShares of companies whose product demand and revenues barely respond to the business cycle — such as medicines and health services — used to reduce a portfolio's unsystematic risk.
- Risk adjusted returnThe return an investment earns for each unit of risk it takes on, rather than the return looked at on its own — in this paper, measured through the Sharpe ratio.
- PortfolioUnder the SEBI PM Regulations, the total holdings of securities and goods belonging to any person — the basket whose return is a weighted average but whose risk also depends on correlation.
- Short hedgeA hedge made by selling futures to protect an existing holding or a planned sale against a price fall — the futures gain offsets the lower cash price, locking in roughly the futures price.
- Hedge ratioThe number of futures (or options) needed to hedge a position. For one stock with its own futures it is 1:1; for a portfolio against index futures it is portfolio value × beta ÷ contract value.
- Cross hedgeHedging an exposure with futures on a different but closely associated asset, because no futures contract exists on the asset itself — for example, hedging a stock portfolio with index futures.
← All terms