Stock Index

What Is a Stock Index?

In 1884, Charles Henry Dow averaged the closing prices of 11 stocks he considered representative of the strength of the U.S. economy in a paper that preceded The Wall Street Journal. By 1896, The Wall Street Journal was publishing this average on a regular basis, and the most famous indicator of stock market performance was born: the Dow Jones Industrial Average (DJIA or Dow).

Most people have heard of the Dow Jones Industrial Average, as well as a few other well-known stock indexes that track the overall direction of the market. Indexes and averages serve as useful benchmarks against which investors can measure the performance of their own portfolios. Depending on its makeup, a stock index can give investors some idea about the state of the market as a whole or a certain sector of the market. Conceptually, a shift in the price of an index represents an equitable change in the stocks included in the index.

Basically, indexes are imaginary portfolios of securities that represent a particular market or section of the market. Each index has its own method of calculating a change in its base value, often expressed as a percentage change. Thus, you might hear that an index has risen or fallen by