Capitalization-weighted index in the context of "NASDAQ-100"

S&P 500 (Standard and Poor's 500) is a stock market index tracking the stock performance of 500 leading companies listed on stock exchanges in the United States. It is one of the most commonly followed equity indices and includes approximately 80% of the total market capitalization of U.S. public companies, with an aggregate market cap of more than $57.401 trillion as of August 29, 2025.

The S&P 500 index is a public float weighted/capitalization-weighted index. The ten largest companies on the list of S&P 500 companies account for approximately 38% of the market capitalization of the index and the 50 largest components account for 60% of the index. As of September 2025, the 10 largest components are, in order of highest to lowest weighting: Nvidia (7.2%), Microsoft (6.3%), Apple (5.9%), Alphabet (5.0%, including both class A & C shares), Amazon (4.1%), Meta Platforms (3.2%), Broadcom (2.8%), Tesla (2.3%), Berkshire Hathaway (1.8%), and JPMorgan Chase (1.4%). The components that have increased their dividends in 25 consecutive years are known as the S&P 500 Dividend Aristocrats. Companies in the S&P 500 derive a collective 72% of revenues from the United States and 28% from other countries.

The Dow Jones Industrial Average (DJIA), Dow Jones, or simply the Dow (/ˈdaʊ/), is a stock market index of 30 prominent companies listed on stock exchanges in the United States.

The DJIA is one of the oldest and most commonly followed equity indices. It is price-weighted, unlike other common indices such as the Nasdaq Composite or S&P 500, which use market capitalization. The primary pitfall of this approach is that a stock's price—not the size of the company—determines its relative importance in the index. For example, as of March 2025, Goldman Sachs represented the largest component of the index with a market capitalization of ~$167B. In contrast, Apple's market capitalization was ~$3.3T at the time, but it fell outside the top 10 components in the index.

The S&P 500 is a stock market index maintained by S&P Dow Jones Indices. It comprises 503 common stocks which are issued by 500 large-cap companies traded on the American stock exchanges (including the 30 companies that compose the Dow Jones Industrial Average). The index includes about 80 percent of the American market by capitalization. It is weighted by free-float market capitalization, so more valuable companies account for relatively more weight in the index. The index constituents and the constituent weights are updated regularly using rules published by S&P Dow Jones Indices. Although called the S&P 500, the index contains 503 stocks because it includes two share classes of stock from three of its component companies (Alphabet, Fox Corporation and News Corp).