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What Is a Stock Index? The S&P 500, Dow and More
What Is a Stock Index? The S&P 500, Dow and More
For investors, an index tracks the performance of a group of assets. The S&P 500 is a well-known stock market index.
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Index Funds vs. Mutual Funds: The Differences That Matter Best Mutual Funds for July and How to Invest The Best ETFs and How to Start Investing 14 Best-Performing and Affordable ESG ETFs for 2026 An index tracks the performance of a group of preselected investments, such as stocks. For example, the S&P 500 index tracks the performance of 500 of the largest U.S. companies. Investors gauge the performance of stocks, bonds or mutual funds by comparing them with the performance of an index. The S&P 500 and the Dow Jones Industrial Average (DJIA or "the Dow") are two of the most well-known stock market indexes. While these indexes track the broad market and large-company stock movements, other indexes may track only a certain industry or sector of the market.Stock index examples
Here are some details on common indexes that investors — as well as a range of index funds and ETFs — follow: 1. S&P 500 Index: The S&P 500 tracks the market moves of around 500 of the largest publicly traded companies in the U.S. The index is a representation of leading companies in leading industries and is capitalization-weighted, which means each stock is weighted proportionately to the company’s market capitalization. For example, a company whose total shares are valued at $100 billion is weighted more heavily than a $10 billion company. (Learn how to invest in the S&P 500.) 1. S&P 500 Index: 2. Dow Jones Industrial Average: The DJIA follows the performance of the 30 largest U.S. companies, also known as “blue chip” stocks. Market capitalization is not considered in this index. There are a few different Dow ETFs that track the index in different ways, depending on your investment goal. 2. Dow Jones Industrial Average: 3. Bloomberg Barclays U.S. Aggregate Bond Index: Also known as the Agg, this is a broad index that tracks the U.S. bond market. The index measures the investment grade, U.S. dollar-denominated, fixed-rate taxable bond market. 3. Bloomberg Barclays U.S. Aggregate Bond Index: 4. Nasdaq Composite Index: The Nasdaq tracks the performance of more than 3,000 companies, with a heavy focus on technology. 4. Nasdaq Composite Index: 5. Russell 2000 Index: This index tracks 2,000 smaller — also known as small-cap — companies. These generally have market capitalizations between $300 million and $2 billion. 5. Russell 2000 Index: » Explore further: What are the best index funds? » Explore further: Brokerage firms Learn more Learn moreon Charles Schwab's website
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