The Dow Jones Industrial Average (DOW) is a stock index that tracks the performance of 30 large publicly traded companies in the United States. It is one of the oldest and most widely followed stock indices in the world, and is often used as a barometer of the overall health of the U.S. stock market. The index is calculated by taking the sum of the prices of the 30 stocks and then dividing it by a divisor, which is adjusted to account for stock splits and other corporate actions.