Dow Jones Industrial Average

The Dow Jones Industrial Average, also referred to as the Industrial Average, the Dow Jones, the Dow 30, or simply the Dow, is a stock market index, and one of several indices created by Wall Street Journal editor and Dow Jones & Company co-founder Charles Dow. It is now owned by the CME Group, which is the majority owner of Dow Jones Indexes. The average is named after Dow and one of his business associates, statistician Edward Jones. It is an index that shows how 30 large, publicly owned companies based in the United States have traded during a standard trading session in the stock market.It is the second oldest U.S. market index after the Dow Jones Transportation Average, which was also created by Dow.

The Industrial portion of the name is largely historical, as many of the modern 30 components have little or nothing to do with traditional heavy industry. The average is price-weighted, and to compensate for the effects of stock splits and other adjustments, it is currently a scaled average. The value of the Dow is not the actual average of the prices of its component stocks, but rather the sum of the component prices divided by a divisor, which changes whenever one of the component stocks has a stock split or stock dividend, so as to generate a consistent value for the index.

Along with the NASDAQ Composite, the S&P 500 Index, and the Russell 2000 Index, the Dow is among the most closely watched U.S. benchmark indices tracking targeted stock market activity. Although Dow compiled the index to gauge the performance of the industrial sector within the American economy, the index's performance continues to be influenced by not only corporate and economic reports, but also by domestic and foreign political events such as war and terrorism, as well as by natural disasters that could potentially lead to economic harm. Components of the Dow trade on both the NASDAQ OMX and the NYSE Euronext, two of the largest stock market companies. Derivatives of the Dow trade on the Chicago Board Options Exchange and through the CME Group, the world's largest futures exchange company, which owns 90% of the indexing business founded by Dow Jones, including the Industrial Average.

( From Wikipedia )