Dow Jones Industrial Average (DJIA)

This is the oldest, most widely quoted index, established in 1896.  It is used by most analysts and reporters to indicate the day-to-day direction of the market.  It is made up of only 30 "Blue Chip" companies (see Stock Labels Mostly Unofficial Stock Classifications), ones that are large, established, and stable.  These 30 companies make up 20-25% of the market value of the U.S. stock market.  Stocks in the index can change if a stock has significant financial difficulty and does not meet the criteria for the average.  The most recent change was in June 2009 when General Motors and Citigroup were replaced by The Travelers Companies and Cisco Systems.  Although it is the most quoted index, some experts dislike the idea of the DJIA since they think the use of only 30 stocks does not show the true picture of the broader market.  Dow Jones also produces other indexes for transportation, utilities, and global markets, to name a few.  Visit their website for more information