Types of Stock Market Indices in India

A stock market index is a number that shows how a selected group of listed companies is performing. If you are wondering what stock market index is, it is a way of measuring the overall movement of shares that belong to a particular market, sector, or category. A stock market index, also called an index in the stock market, is created by combining selected stocks using a defined calculation method, such as market capitalisation or share price. It provides a simple representation of how that group of companies has moved over a given period.

There are different types of stock indices that help track the performance of the overall market as well as specific sectors and groups of companies. These types of market indices are classified based on factors such as market coverage, sector, market capitalisation, and investment focus. Below are the categories of stock market indices in India and around the world:

Benchmark Indices – These are widely used as reference indices and generally represent the performance of the broader market.

Examples: Nifty 50, Sensex

Sectoral Indices – Measure the performance of specific industries, such as Nifty IT, Nifty Pharma, and Nifty Bank.

Market Capitalisation-Based Indices – Classify companies according to their market capitalisation, such as large-cap, mid-cap, and small-cap indices.

Thematic and Other Indices – Track companies that follow a particular theme, focus area, or sector.

Examples: Nifty ESG, Nifty India Consumption.

The calculation method varies by index type but generally includes:

• Aggregation of stock prices or market capitalisation

• Weighting factors (market cap, price or equal weighting) applied

• Use of a divisor to maintain continuity despite stock splits, dividends, or corporate actions
   

The divisor ensures that the index value remains consistent after corporate actions like stock splits or dividends, reflecting only the actual market change.

Market-Cap Weighted Index Formula (Simplified)

Index Value = (Sum of Market Caps of constituent stocks) / Divisor

Price Weighted Index Formula (Simplified)

Index Value = (Sum of stock prices) / Divisor

The divisor is adjusted for corporate actions such as stock splits, dividends, and mergers to maintain index continuity and prevent distortions.

Note: Indices may also be reviewed and rebalanced periodically to reflect changes in constituent eligibility, free-float market capitalisation, liquidity, and other criteria specified in the index methodology.

According to index methodology published by stock exchanges, stock market indices are influenced by factors such as constituent stock prices, corporate actions, and broader market movements.

• Economic data points and macroeconomic trends – Inflation, GDP growth, and interest rates influence overall market direction.

• Sector performance and company earnings – Higher or lower earnings results within industries may affect corresponding indices.

• Market sentiment and investor behaviour – Positive or negative outlooks drive short-term index movements.

• Regulatory changes and policy decisions – Government policies, reforms, and global regulations impact index values.

• Corporate actions – Events such as stock splits, mergers, bonus issues, and dividends may affect constituent weights or require index adjustments in accordance with the index methodology.
   

Together, these factors influence changes in index values, which are commonly used to represent market movements.

Stock market indices provide a structured way to represent the performance of selected companies, sectors, or segments of the market. Stock market indices are grouped by weighting method, market capitalisation, and sector. Each type applies a different rule for assigning weight to its constituents, which determines how the index value is calculated. Awareness of these different types of indices provides context for understanding how market performance is represented without implying any investment direction.