The Dow Jones is one of the oldest benchmarks in investing. Introduced in 1896, the index remains a popular benchmark for measuring the economy. There’s certainly more to measuring the economy than a single benchmark, but investors have used it as a gauge for many years.The index has undergone many changes since its introduction in 1896. It originally consisted of 12 companies and was expanded to 30 companies in 1928. Some of the 1928 Dow Jones companies are still in business, while others are corporate gia ...