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An Introduction To Stock Market Indexes
June 04 2011| Filed Under » Index Fund, Investing Basics, Stocks
Its not unusual for people to talk about the market as if there were a common meaning for the word. But in reality, the many indexes of the differing segments of the market dont always move in tandem. If they did, there would be no reason to have multiple indexes. By gaining a clear understanding of how indexes are created and how they differ, you will be on your way to making sense of the daily movements in the marketplace. Here well compare and contrast the main market indexes so that the next time you hear someone refer to the market, youll have a better idea of just what they mean.
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The Dow
If you ask an investor how the market is doing, you might get an answer that is based on the Dow. The Dow Jones Industrial Average (DJIA) is one of the oldest, most well-known and most frequently used indexes in the world. It includes the stocks of 30 of the worlds largest and most influential companies. The DJIA is whats known as a price weighted index. It was originally computed by adding up the per-share price of the stocks of each company in the index and dividing this sum by the number of companies - thats why its called an average. Unfortunately, it is no longer this simple to calculate. Over the years, stock splits, spin-offs and other events have resulted in changes in the divisor, making it a very small number (less than 0.2).
The DJIA represents about a quarter of the value of the entire U.S. stock market, but a percent change in the Dow should not be interpreted as a definite indication that the entire market has dropped by the same percent. This is because of the Dows price-weighted function. The basic problem is that a $1 change in the price of a $120 stock in the index will have the same effect on the DJIA as a $1 change in the price of a $20 stock, even though one stock may have changed by 0.8% and the other by 5%.
A change in the Dow represents changes in investors expectations of the earnings and risks of the large companies included in the average. Because the general attitude toward large-cap stocks often differs from the attitude toward small-cap stocks, international stocks or technology stocks, the Dow should not be used to represent sentiment in other areas of the marketplace. On the other hand, because the Dow is made up of some of the most well-known companies in the U.S., large swings in this index generally correspond to the movement of the entire market, although not necessarily on the same scale. (For more information on this index, see Calculating The Dow Jones Industrial Average.)
The S
