Composite Indexes: A Comprehensive Guide to Understanding, Types, and Significance


Explore the world of composite indexes in-depth. Learn how these statistical tools combine equities, securities, or indexes to assess market and sector performance. Discover their various types, methodologies, and the role they play in investment analysis and economic trend measurement.

Composite indexes serve as powerful tools in the world of finance, allowing us to consolidate various equities, securities, or indexes. These indexes play a pivotal role in assessing and interpreting the performance of markets and sectors. In this comprehensive guide, we will delve into the intricate world of composite indexes, examining their types, methodologies, and their significance in investment analysis and economic trend measurement.

Understanding a composite index

Composite indexes serve multiple purposes and are indispensable in the financial landscape:

  • Investment analysis: Composite indexes are instrumental in evaluating the performance of investment portfolios. By comparing your portfolio against these benchmarks, you can gain insights into how your investments are faring against broader market trends.
  • Economic trend measurement: Economists and analysts use composite indexes to monitor and analyze economic trends. By studying the performance of various assets or sectors over time, they can draw valuable conclusions about the economy’s health.
  • Market activity forecasting: These indexes are used to predict market activity by closely following their movements. Analysts can make informed predictions about future market trends based on the historical performance of composite indexes.

The primary goal of a well-diversified portfolio is often to outperform the major composite indexes. In the United States, three composite indexes dominate the landscape: the Nasdaq Composite, Dow Jones Industrial Average (commonly known as the Dow), and the Standard & Poor’s 500 Index (S&P 500).

Types of composite indexes

The Nasdaq composite

The Nasdaq Composite, established in 1971 with just 50 companies, has evolved into a comprehensive index that includes over 3,000 individual equities listed on the Nasdaq Stock Market. It follows a market capitalization (market cap)-weighted methodology.

Standard & poor’s 500 index (S&P 500)

The S&P 500 is widely regarded as a benchmark for large U.S. equities. It comprises the 500 largest publicly-traded U.S. companies by market value and also follows a cap-weighted index methodology.

Dow Jones industrial average

The Dow Jones Industrial Average, often referred to simply as “the Dow,” takes a unique approach as a price-weighted composite index. When you hear the news stating “the market is up,” they are typically referring to the Dow.

Cap-weighted index vs. price-weighted index

A crucial distinction exists between cap-weighted and price-weighted indexes:

Cap-weighted index: In cap-weighted indexes, each component’s total market capitalization proportionally influences the index’s level. Components with higher market capitalization hold more sway over the index’s performance.

Cap-weighted index

Calculating the total market capitalization of a cap-weighted index involves multiplying the price per share of each company by its total number of shares outstanding.

For example:

  • Stock A: Price per share equals $25, and total shares outstanding equal 1,000,000. This results in a market cap of $25,000,000.
  • Stock B: Price per share equals $50, and total shares outstanding equal 500,000, equating to a market cap of $25,000,000.
  • Stock C: Price per share equals $50, and total shares outstanding equal 1,000,000, resulting in a market cap of $50,000,000.

The composite’s total market capitalization would be $100,000,000. Stock A’s weight would be 25%, Stock B’s weight would be 25%, and Stock C’s weight would be 50%. Typically, an index divisor is used to make the index manageable for reporting purposes. In this case, the divisor would be $100,000, and the initial composite level would be equal to $100,000,000 / $100,000 = 1,000.

Price-weighted index

Price-weighted indexes take a different approach. Components are weighted based solely on their prices, not on market capitalization or shares outstanding. Each stock’s influence on the index corresponds directly to its price per share.

Example of a price-weighted composite index
In this scenario, components are weighted by price, not by market capitalization or shares outstanding. Each stock’s impact on the index is proportionate to its price per share. For instance:

  • Stock A: Price equals $3.
  • Stock B: Price equals $6.
  • Stock C: Price equals $30.
  • Stock D: Price equals $10.
  • Stock E: Price equals $1.

To determine the composite level, add the components and divide that sum by the number of components. In this case, the composite level would be $10 ($50 / 5 = $10).

Pros and cons


Here is a list of the benefits and drawbacks to consider.

  • Effective benchmark for investment portfolios.
  • Provides insight into economic trends.
  • Useful for forecasting market activity.
  • May not reflect the entirety of a diverse market.
  • Fluctuations can be influenced by a few heavily weighted components.

Frequently asked questions

What are the main composite indexes in the United States?

The primary composite indexes in the United States include the Nasdaq Composite, Dow Jones Industrial Average, and the Standard & Poor’s 500 Index.

Can I create my own composite index for a specific sector or group of stocks?

Yes, you can create a custom composite index to track the performance of a specific sector or group of stocks. Many financial tools and software platforms offer this functionality.

How are sector-specific composite indexes created?

To create a sector-specific composite index, you would select a group of stocks that represent that sector. The index’s performance is calculated based on the price changes of these chosen stocks over time.

What role do composite indexes play in ETFs?

Composite indexes are often used as the benchmark for exchange-traded funds (ETFs). ETFs aim to replicate the performance of a specific index, providing investors with diversified exposure to a range of assets or sectors.

Key takeaways

  • Composite indexes serve as crucial tools in investment analysis, economic trend measurement, and market forecasting.
  • The Nasdaq Composite, S&P 500, and Dow Jones Industrial Average are the prominent U.S. composite indexes.
  • Cap-weighted and price-weighted indexes differ in their methodologies for determining index levels.
  • When using a composite index for investment analysis, consider both its advantages and limitations.
  • Investors can create their own composite indexes to track specific sectors or groups of stocks.
View Article Sources
  1. Composite Index Construction with Expert Opinion – Journal of Business & Economic Statistics
  2. Composite Indexes and Systems of Indicators of Regional Integration – United Nations University
  3. Composite Indices of Human Well-being – United Nations University World Institute for Development
  4. Stock Market Indexes – SuperMoney
  5. What Is a Broad-Based Index, and What Are Some Broad Index Funds – SuperMoney