Traders now have some new Dow firms to monitor

American International, Pfizer and Verizon have been added to the index, replacing AT&T, Eastman Kodak and International Paper.

The Dow Jones - which has been running since 1896 - tracks the share movements of 30 companies.

Changes to the widely-watched index reflect trends within the US economy.

Pfizer is the world's biggest drugs company, American International is the world's largest insurer and Verizon Communications - formed by the merger of GTE and Bell Atlantic - is one of the world's leading providers of landline and wireless communications.

Historical significance

The flagship US share index has long been seen as America's economic barometer.

Some professional investors point to the limited range of the 30-stock Dow, but individual investors around the world have continued to use it as a "health" index of the US economy, shunning the wider S&P 500.

When it started it had just twelve companies, with General Electric the only original member still in the index. The index expanded to cover 30 firms in 1928.

Its origin as a measure of industrial companies became more blurred as financial corporations American Express, JP Morgan and Citigroup joined between 1982 and 1997.