Dow Jones industrial average

One of the oldest and best-known stock market indicators. The Dow Jones is an index of 30 blue-chip US stocks. The unweighted index was founded in 1896 with just 12 stocks, and increased to 30 in 1928. The index value is arrived at by totalling the stock prices and dividing by a specially calculated divisor.

The stocks that make up the index are chosen by the editors of The Wall Street Journal and are a barometer of the economic health of the USA. Changes are fairly infrequent; Sears, Roebuck, & Co., for example, was replaced only in 1999, having entered the index in 1924. Several companies have dipped in and out of the index as their fortunes have waxed and waned. General Electric, one of the original 12 stocks, has been in and out twice, and IBM was ejected in 1939 but readmitted in 1979.