NISM-Series-VIII: Equity Derivatives · Understanding Index

Features of a Good Index and Index Management Explained

Updated 11 October 2026 · Fact-checked

A good index represents the market it tracks, uses liquid and investable stocks, is transparent, rule-based and stable, and can be replicated cheaply. Index management keeps it true to that purpose: maintenance handles routine changes, rebalancing resets weights, and reconstitution replaces constituents. In the exam, match each feature or activity to its definition.

Understand Features of Good Index and Index Management

An index is a single number that summarises the movement of a group of securities. Investors use it to judge market performance, to benchmark funds, and as the base for index funds, ETFs, futures and options. Because so much depends on it, the index must be built well.

A good index has these features:
- Representativeness: it reflects the market or sector it claims to track, usually by covering a large share of its market capitalisation.
- Liquidity: constituents trade actively, so the index can be tracked and the stocks bought or sold at fair prices. Low liquidity makes prices easy to distort.
- Investability and replicability: investors can actually hold the stocks in index proportions with low cost.
- Transparency and rule-based methodology: selection and weighting rules are public and applied consistently, not by personal judgement.
- Stability: the index should not change too often, which keeps turnover and tracking cost low.
- Diversification: no single stock or sector should dominate unduly.
- Low manipulation risk: it should be hard for a few traders to move it.

Index management is the upkeep of an index after launch. Index maintenance is the day-to-day work: adjusting for corporate actions such as splits, bonus issues, rights issues, mergers and demergers, so the index value does not jump for reasons unrelated to market prices. An index divisor or similar adjustment is used to keep the level continuous.

Rebalancing means resetting the weights of the existing constituents back to the intended weights, for example when prices have moved them away from target, or when the free-float or share count has changed. It is done at a set frequency. Reconstitution means changing the list of constituents: removing stocks that no longer meet the criteria and adding those that do. Exchanges such as NSE have an index committee that reviews indices periodically (the Nifty 50 is reviewed semi-annually) and applies published criteria like liquidity, free-float market capitalisation and eligibility for the derivatives segment. Do not memorise more detail than your workbook states.

A simple way to remember: maintenance keeps the number continuous, rebalancing fixes the weights, reconstitution fixes the members.

Key formulas to remember

Features of a good index: Representative + Liquid + Investable + Transparent + Stable + Diversified; Typical attributes tested. Representativeness and liquidity are the most commonly asked.
Index maintenance: Adjust for corporate actions so the index level stays continuous; Covers splits, bonus, rights, mergers, demergers. Not a change of constituents.
Rebalancing: Reset weights of existing constituents to target; Constituent list stays the same.
Reconstitution: Add or remove constituents as per eligibility criteria; Done periodically after review by the index committee under published rules.

How to solve Features of Good Index and Index Management questions

Use this method for any definition, feature or scenario question on index quality and upkeep.

1Read the stem and decide whether it asks about a feature of a good index or an index management activity.
2If it is a feature, find the keyword: coverage of market means representativeness; ease of trading means liquidity; replication means investability; public rules means transparency.
3If it is management, ask: did the stock list change? If yes, it is reconstitution.
4If the list is the same but weights are reset, it is rebalancing.
5If the cause is a corporate action and the aim is a continuous index level, it is maintenance.
6Eliminate options that say the index should change constituents very frequently or be based on discretion without rules.
7Choose the option that matches the exact term, and check that no word like 'always' or 'only' makes it wrong.

Quickest way: Three-question test

When to use it: When you have under a minute and options look similar.

Did the members change? Yes means reconstitution.
Did only weights reset? Yes means rebalancing.
Was it a corporate action adjustment for continuity? Yes means maintenance.
For features, pick the one whose keyword matches: market coverage, trading ease, replication, rules, stability.

Common mistakes in Features of Good Index and Index Management

Using rebalancing and reconstitution as the same thing.
Both are periodic reviews and sound alike.
Fix: Rebalancing changes weights only. Reconstitution changes the list of stocks.
Thinking a good index should change constituents often to stay current.
Students link being up to date with frequent change.
Fix: Stability is a feature. Frequent change raises turnover and tracking cost for index funds.
Treating liquidity as only high returns or high price.
Confusing liquid with valuable.
Fix: Liquidity means stocks trade easily with low impact cost, which makes the index investable and hard to manipulate.
Believing maintenance means replacing stocks.
The word sounds like general upkeep.
Fix: Maintenance is mainly adjusting for corporate actions to keep the index level continuous.
Picking discretionary selection as a feature of a good index.
Assuming expert judgement is better.
Fix: A good index uses transparent, published, rule-based criteria.

Worked examples

Example 1

An index provider removes a stock that no longer meets the liquidity criteria and adds a new eligible stock. This activity is called: (A) Index maintenance (B) Index rebalancing (C) Index reconstitution (D) Index divisor adjustment

Show the solution

The list of constituents changed: one out, one in.
A change of members is reconstitution.
Rebalancing would keep the same stocks and reset weights.
Maintenance relates to corporate action adjustments.

Answer: (C) Index reconstitution

Example 2

Which of the following is NOT a feature of a good index? (A) Transparent methodology (B) Representative of the market (C) Constituents selected at the discretion of one person without published rules (D) Adequate liquidity of constituents

Show the solution

Check each option against the known features.
A, B and D are all listed attributes: transparency, representativeness, liquidity.
Option C is discretionary and non-transparent, which goes against a rule-based methodology.

Answer: (C) Discretionary selection without published rules is not a feature of a good index.

Exam tips

Learn the one-line definitions of maintenance, rebalancing and reconstitution; most questions test only these.
Representativeness and liquidity are the headline features, so know them cold.
Watch for 'NOT' and 'EXCEPT' in the stem.
Do not memorise review dates beyond what the workbook states; focus on the concept.
In a negatively marked paper, skip only if two options remain equally likely after elimination.

Practice questions from Understanding Index

Features of Good Index and Index Management in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

CMA FinalPricing of Stock and Index Futures

Features of Good Index and Index Management: frequently asked questions

What are the features of a good stock index?

A good index is representative of the market, made of liquid stocks, investable, transparent and rule-based, stable and diversified. These make it reliable as a benchmark and usable for funds and derivatives.

What is the difference between index rebalancing and reconstitution?

Rebalancing resets the weights of the existing constituents. Reconstitution changes which stocks are in the index. Both are done as per the index methodology.

How are index constituents selected by NSE?

NSE indices use published, rule-based criteria such as free-float market capitalisation, liquidity and, for headline indices, eligibility for the derivatives segment. An index committee reviews the indices periodically.

What is index maintenance?

It is the ongoing adjustment of an index for corporate actions like splits, bonus issues, rights and mergers, so the index level does not change for reasons unrelated to market movement.