Definition
Index Construction
Index construction is the set of rules defining how an index is built, including eligibility criteria, weighting scheme, number of constituents and selection thresholds for liquidity and size.
An Indian index's methodology specifies criteria such as listing history, free-float market cap rank, impact cost limits and trading frequency for inclusion. The Nifty 50, for instance, selects large, liquid stocks meeting impact-cost and free-float thresholds, weighted by free-float market cap.
Clear, published construction rules make an index investable and replicable, letting passive funds mirror it with low tracking error. Methodology choices, cap-weighting versus equal-weighting, single versus multi-factor, capping rules, fundamentally shape an index's risk, concentration and turnover.
Related terms
- Free-float Market CapitalisationFree-float market capitalisation values a company using only the shares available for public trading, excluding locked-in holdings of promoters, governments and strategic investors.
- Index MethodologyIndex methodology is the detailed, published rulebook governing how an index selects, weights, caps and reviews its constituents, ensuring the index is transparent, replicable and consistent over time.
- Index RebalancingIndex rebalancing is the periodic adjustment of constituent weights back to their methodology-defined levels, accounting for price moves, capping limits and corporate actions, without necessarily changing the membership.
- Capping (Index)Capping is an index rule that limits the maximum weight any single constituent, or group such as a sector, can have, preventing excessive concentration and ensuring diversification.
Plain-English explainer from The Dispatch Investors Encyclopedia. General information, not financial advice.