What Is the Dow Jones?

If you watch the news, you’ve no doubt heard mention of the Dow Jones Industrial Average. Simply put, the DJIA is a number published daily by Dow Jones and Company that represents the average value of 30 large industrial stocks traded on the New York Stock Exchange.

The Dow’s purpose is

to take the stock market’s temperature, so to speak. If the economy is doing well, stock prices as a group tend to rise. If it’s doing poorly, prices as a group tend to fall. If a specific stock is going down while the market as a whole is going up, that tells you something. And if a stock is rising but is rising faster or slower than the market as a whole, that tells you something as well.

With so many other stock indexes being published, such as the S&P 500, you might wonder why the DJIA is so often quoted in the news. The answer has to do with history and familiarity. Although today the Dow is comprised of 30 companies’ stock prices, when it was first published in May 1896 by Charles H. Dow it was made up of only 12 companies. Of those 12 companies, General Electric is the only company that remains on the list today. The Dow was expanded to 20 stocks in 1916 and then to 30 stocks in 1928. With such a long history it's easy to compare the stock market of today with the stock market of, say, 1930.

If you were to add the stock prices of the 30 companies in today’s DJIA, you'd find that it doesn’t equal the DJIA published. That’s because the Dow is calculated using something called the “divisor” method. Before the divisor method was introduced in 1928, the index was figured by adding the price of each stock and dividing by the number of stocks. However problems began to arise when companies were added and removed from the list and when stock splits (one share becoming two or three shares) occurred. The divisor method can be a complicated one but it allows for stock index value comparisons across time.

The 30 companies account for more than 25 percent of the market value of all 3,000 stocks traded on the New York Stock Exchange. And for those who need a more rounded summation of the stock market’s health, there’s the Dow Jones Transportation Average, which includes 20 different stocks of railroad, trucking, and airline companies, and the Dow Jones Utility Average, which includes 15 electric, gas, and other utility companies.

The editors of The Wall Street Journal select the stocks listed in the DJIA, in part by taking a broad view of what “industrial” means. For Dow purposes, industrial means virtually any company that isn't a utility or in the transportation business. Remember, there are separate Dow Jones averages for those kinds of stocks.

In choosing a new company for the DJIA, they search for substantial industrial companies that possess both a history of successful growth and wide investor interest. Dow components are rarely changed because the Dow isn't a "hot stock" index, and the Journal editors indicate that stability of composition enhances the trust many people have in the averages. The most frequent reason for changing a stock is that something is happening to one of the components, such as a takeover. Whenever one stock is changed, the rest are reviewed.

Neither the DJIA nor any other index should be considered a prediction of where the stock market is headed. Rather they are reflections of where the market has been. And as to how high it can climb, there are no mathematical limitations to the industrial average's ascent. Also keep in mind that no matter how large the numbers, it’s the market's trend at any given time that is important.