Dow Jones

Dow Jones Industrial Average (DJIA) is one of the stock market index established by the editor of The Wall Street Journal and Dow Jones & Company founder Charles Dow. Dow makes this index as a way to measure the performance of the component industry in the U.S. stock market. Today the DJIA is the oldest U.S. market index is still running.
Now, the stock market consists of the 30 largest companies in the United States are already widely publicly. To compensate for the effects of stock splits and other adjustments, is now using a weighted average. not the actual average price of the stock components.
Initially in 1896 there were 12 companies listed in the DJIA. The number of stock exchange membership and then propagated to 20 in 1916, and finally to 30 companies since 1928 until now. Editor of the newspaper The Wall Street Journal choose which company will be issued and put into stock.