This index, the most widely known, and widely regarded, benchmark of the U.S. equities market, compares the performance of a representative sample of 500 "large-cap" companies in leading industries of the U.S. economy. The S&P 500 is maintained by the S&P Index Committee, whose members include economists and analysts. The committee rates stocks based on their size, their liquidity, or availability of assets, their rank in their industry, and how diversified they are. The S&P 500 is frequently used as the standard of comparison in determining a stock's investment performance.

The DJIA, or Dow Jones Industrial Average. If you want to buy a "blue-chip" stock, which are stocks known for their ability to make money and pay dividends to shareholders, then this is the index to compare it to.

This index measures 30 "blue-chip" stocks, which get their fancy name from the companies they represent. These are large, creditworthy companies traded in the U.S. that are famous for their quality and the wide acceptance of their products and services. By studying these companies, many believe one can get a good picture of how the market as a whole is performing.

This index, prepared and published by Dow Jones & Co., is one of the oldest market indicators. The companies within the Dow are widely held by individuals and institutional investors. The Dow's 30 stocks represent about a fifth of the $8 trillion-plus market value of all U.S. stocks, and about a quarter of the value of stocks listed on the New York Stock Exchange. Although there are now dozens of alternatives, the Dow is still the index financial professionals instinctively check first to see how "the market" is doing. It has a wide following among investors and is well known by even those who have yet to invest in equities.

NASDAQ Composite Index. If you're looking for an index that contains companies whose common characteristic is size, or "market capitalization," measured according to the total dollar value of all outstanding shares, check out this index.

The NASDAQ Composite Index looks at the market capitalization of both domestic and international stocks. Because it is so broad-based and evaluates more companies (over 4,000) than most other stock market indices, the NASDAQ is also widely followed and quoted among the major market indices.

Russell 3000® Index. If you're looking at a stock from a new and growing company, this is the index to compare it to.

The Russell 3000 Index, which represents 98% of the U.S. market, provides a barometer of the broad market and is revised annually to include new and growing equities.

Russell 2000 Index. If you're looking at stock from a "small-cap" company (a company with less than $1 billion in the stock market), this is the index to compare it to.

The Russell 2000 Index, which includes the smallest 2000 securities in the Russell 3000, offers investors access to "small-cap" companies. Like the Russell 3000, this index is also revised annually to include this part of the market.

The Dow Jones Wilshire 5000 Index. This index, the largest of the indices, measures the performance of nearly all U.S. companies. This means you could compare any stock to this index, especially those that don't have any of the characteristics of the above indices.