Below you'll find data, news, component listings and other information on some of the most important U.S. market indices. Given how frequently they are cited in the financial press, as well as how many trillions of dollars are tied to these major indices, it's important to understand each index and its component securities...

Dow Jones Industrial Average
The Dow Jones Industrial Average is probably the best-known and most widely followed index in the world.  The index consists of 30 of the largest publicly traded firms in the United States.

S&P 500
The S&P 500 index is probably the most commonly referenced U.S. equity benchmark. This diverse index comprises over 70% of the total market cap of all stocks traded in the U.S.

Nasdaq Composite
The Nasdaq Composite is a broad market index that encompasses about 4,000 issues traded on the Nasdaq National Market--virtually every firm that trades on the exchange

Nasdaq 100
The Nasdaq 100 Index is comprised of the 100 largest stocks (based on market capitalization) traded on the Nasdaq National Market. Because it tracks stocks traded on the Nasdaq exchange, it is often considered a technology barometer despite the fact that many healthcare, biotech, and service issues trade there as well.

Wilshire 5000
The Wilshire 5000 is considered the "total market index." Designed to track the value of the entire stock market, the index actually contains around 6,700 stocks today.

S&P MidCap 400
The S&P MidCap 400 Index tracks a diverse basket of medium-sized U.S. firms. A mid-cap stock is broadly defined as a company with a market capitalization ranging from about $2 billion to $10 billion.

S&P SmallCap 600
The S&P SmallCap 600 Index invests in a basket of small-cap equities. A small-cap company is generally defined as a stock with a market capitalization between $300 million and $2 billion.

Russell 3000
The Russell 3000 Index attempts to capture the return of the overall market, and is comprised of the 3000 largest and most liquid stocks based and traded in the U.S.

Russell 2000
The Russell 2000 Index is a subset of the larger Russell 3000. It is one of the most widely used indexes by investors and is generally accepted as the benchmark for small-cap firms.

Russell 1000
The Russell 1000 is designed to track the performance of most major large-cap companies. The index is a subset of the much larger Russell 3000 Index--it simply contains the 1000 largest stocks within that index. The components of the Russell 1000 Index account for about 90% of the equity traded on the U.S. exchanges.