Top 10 Stocks in the Standard & Poor's 500

The Standard & Poor's 500 (otherwise known as the S&P 500) is a stock index that is comprised of 500 stocks that are domiciled in the United States (their headquarters are in the U.S.).  Stocks represented in the index are large- and mid-sized companies, many of which are readily recognizable to most U.S.-based (and international) investors.  The index is "cap weighted".  "Cap" is short for market capitalization.  Market cap is the number of shares of common stock outstanding, multiplied by the stock's price.  As of Friday, the largest company, Exxon Mobil, had a market cap of $417.96 billion.  Johnson & Johnson, the 10th largest company in the index, had a market cap of $165.64 billion.  So Exxon Mobil's market cap is 2.5 times as big as Johnson & Johnson's meaning that a 1% change in Exxon Mobil's market cap has 2.5 times as big an impact on the S&P 500's value as does a 1% change in Johnson & Johnson's.  The smallest company in the index has a market cap of 1.63 billion, making Exxon Mobil 256.4 times as important to the S&P 500 as the smallest company.

The top 10 stocks in the S&P 500 as of Friday, with their Economic Sector shown in parentheses, are:

Exxon Mobil (Energy)
Apple Computer (Information Technology)
Chevron (Energy)
General Electric (Industrials)
International Business Machines (Information Technology)
MicroSoft (Information Technology)
A,T&T (Telecommunications Services)
Procter & Gamble (Consumer Staples)
JP Morgan (Finance)
Johnson & Johnson (Health Care)

So when you see a big move in one of these top 10 stocks, chances are, the S&P 500 will move a lot, and in the same direction of the stock's price change.  Note that Energy has 2 representatives, Information Technology has 3 representatives, Industrials, Telecommunications Services, Consumer Staples, Finance and Health Care each have 1 representative.  Materials (papers, chemicals, and metals producers, etc.), Electric Utilities (e.g. Duke Energy) and Consumer Durables (e.g. retailers, auto companies, clothing manufacturers, restaurants) are not represented in the top 10.