Stock Index

What is Stock Index?

Stock index which is also known as the stock market index is a tool used to determine the performance of shares/securities in the market and to calculate the return on the stock of their investment and it is used by investors to have knowledge about the performance of investments and access the total value they possess.

Indexes are often used as a benchmark against which performances of Mutual FundMutual FundA mutual fund is an investment fund that investors professionally manage by pooling money from multiple investors to initiate investment in securities individually held to provide greater diversification, long term gains and lower level of more and ETF’s are compared. The index is further used as investment decisions before adjusting the portfolio. E.g., several Mutual Funds compare their returns to the return in the S&P 500, displaying to the investors how their funds are performing in tandem with respect to the index.

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List of Top 5 Types of Stock Index

Below is the list of top stock indices –

5 Types-of-Stock-Index

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#1 – Standard & Poor 500 (S&P 500)

S&P 500 is a large and diverse index made up of 500 of the most widely traded stocks, especially in the USA. Since the USA is an epicenter of the financial activities impacting across the world, this index gives a good indication of movement in the US as a marketplace. It is market-weighted (capitalization-weighted); each stock is represented in proportion to its market capitalizationMarket CapitalizationMarket capitalization or market cap is the total market value of all the outstanding shares and is calculated by multiplying the outstanding shares with the current market price. Investors use this ratio to determine the company's size rather than using total sales or total more. Thus, if the total market value of all 500 companies in the S&P 500 increases by 6%, the value of the index also increases by 6%.

Firms from various sectors are included in this index, such as:

  • Financial sector
  • Healthcare
  • Industrials
  • Information Technology
  • Consumer Staples
  • Energy
  • Media


It’s an index of the US that measures the performance of around 3,000 companies, including foreign companies. Predominantly known for technology-based companies such as Google, Apple, and other firms in the growth stages, the NASDAQ also measures stocks from other sectors such as:

  • Industrial
  • Insurance
  • Transportation
  • Energy

The value of NASDAQ is computed on the company’s outstanding stock, i.e., market capitalization average of multiple firms part of the index. Therefore the performance of NASDAQ is directly proportional to the performance of the technology sector. There are 3 different market tiers, namely:

  1. Capital market (Small-cap): An equity market for firms with small levels of market capitalization and requirements for listing is less stringent.
  2. Global Market (Midcap) includes around 1,500 stocks representing Nasdaq global markets and are required to meet strict financial and liquidityLiquidityLiquidity shows the ease of converting the assets or the securities of the company into the cash. Liquidity is the ability of the firm to pay off the current liabilities with the current assets it more requirements. There are certain Corporate Governance Standards that have to be met.
  3. Global Stock Market (Large Cap) is a market capitalization-weighted index made up of US-based and international stocks. It is required to meet more stringent requirements as compared to the mid-capMid-capMid-Cap stocks are the stocks of the companies having medium market capitalization. Their capital lies between that of large and small cap companies and valuation of the entire share holdings of these companies range between $2 billion to $8 more and relatively exclusive in comparison to others. The listing department will regularly review the performance and associated rules governing these stocks.

#3 – DJIA (Dow-Jones Industrial Average)

The DJIA is one of the oldest and well-known indices globally, comprising 30 major companies belonging to the industry leaders, which significantly contribute to the industry and stock market. The Dow is a price-weighted average stock market index indicating that any type of stock splitStock SplitStock split, also known as share split, is the process by which companies divide their existing outstanding shares into multiple shares, such as 3 shares for every 1 owned, 2 shares for every 1 held, and so on. The company's market capitalization remains unchanged during a stock split because, while the number of shares grows, the price per share decreases more or adjustment is not considered in the average price computation.

Since it represents a large section of the US market, a percent change in the Dow should not be interpreted as an equal chance in the overall market. It is due to the price-weighted function. E.g., if the value of one stock falls from say $450 to $50, the entire stock market index may fall by around 3,000 points since the quantum of one stock weighs heavily on the base of 30 firms. As the index consists of some of the well-established companies in the US, large swings in the index can generally correspond to the entire market movement, though not necessarily on the same scale.

#4 – FTSE 100 Index (Financial Times Stock Exchange)

This index consists of 100 companies listed on the London Stock Exchange with the highest market capitalization, which is maintained by the FTSE Group (the subsidiary of the London Stock Exchange Group). Many of these 100 firms are internationally focussed and hence may not be the best indicator of the UK economy is functioning and are significantly impacted by the exchange rate of the Pound. The FTSE 250 stock market index could be considered since it includes a smaller proportion of international firms.

The share prices are weighted by market capitalization so that larger firms make more difference to the index instead of the smaller ones. The basic Stock Index formula is:

Stock Index - Formula

The free float adjustment factor is the percentage of all issued sharesIssued SharesShares Issued refers to the number of shares distributed by a company to its shareholders, who range from the general public and insiders to institutional investors. They are recorded as owner's equity on the Company's balance more readily available for trading. The free float market capitalizationFree Float Market CapitalizationFree Float Market Capitalization is a method by which the market cap of an index’s underlying are calculated. It is calculated by multiplying the price with the number of outstanding shares available for investors and more of a company is calculated using the Market cap (number of shares * share price) and multiplied by the free-float factor. It does not include restricted stock units held by insiders such as ESOP’s.

#5 – Russell Indexes

This index is a family of global equity indices from FTSE Russell, permitting investors which track the performances of specific market segments. Many mutual funds or ETFETFAn exchange-traded fund (ETF) is a security that contains many types of securities such as bonds, stocks, commodities, and so on, and that trades on the exchange like a stock, with the price fluctuating many times throughout the day when the exchange-traded fund is bought and sold on the more fund managers use FTSE Russell as benchmarks for measuring their respective performances. The most established index in the series is Russell 2,000, which exclusively tracks the US small-cap stocks of the Russell 3,000 stocks. The participants of the Russell 3,000 and its subsets are determined every year during the annual reconstitution with quarterly enhancements, including any IPO’s. The top 1,000 companies are the large-cap ones, and the others are the small-cap stocks.

The stock index has a rule-based and transparent process for forming the index by listing all firms in a descending order by market capitalization adjusted for the float (actual number of shares available for trading).

Final Thoughts

The stock index also referred to as the stock market index, is an indicator of how securities of a section are performing. It’s a tool used by financial managers and investors for describing the market condition and compare the return on specific investments. The indexes are relatively easier to interpret and indicate live performance, increasing their importance around the world.

It has generally used a benchmark around the world to give a quick indication of how the stocks are performing across sectors. The movement also has a widespread impact on other macroeconomic factors such as Political and overall economy as well.

The stock index gives a quick indication of the direction in which the market is moving and also which industry/company is driving the change.

Stock Index Video

This article has been a guide to what is a stock index? Here we discuss the top 5 stock market index, including the S&P 500, NASDAQ, DJIA, FTSE 100, and Russel Indexes. You may learn more about stock markets from the following suggested articles –

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