<p>The Dow 30, or simply the Dow, is a stock market index that tracks the performance of 30 large, publicly-owned companies traded on the NASDAQ or New York Stock Exchange. It is one of the oldest and most widely followed indices, providing a snapshot of the U.S. economy.</p>

<h2>How It Works</h2>
<p>The Dow 30 is a price-weighted index, meaning each component's price influences its movement. The index's total is calculated by adding the prices of all 30 stocks and then dividing by a divisor, which adjusts for stock splits and changes in component companies.</p>
<p>The 30 components are selected by the editors of the Wall Street Journal based on factors such as size, industry, and financial health. Changes to the index are infrequent, with the last change occurring in August 2020.</p>

<h2>Why It Matters</h2>
<p>The Dow 30 is a key indicator of U.S. stock market performance. It is often used as a benchmark by investors and financial professionals to compare performance and make investment decisions. For example, if the Dow 30 increases by 100 points, it indicates that the average price of the 30 stocks has increased by $100.</p>
<p>Moreover, the Dow 30's components are often considered bellwethers of their respective industries. Changes in their stock prices can provide insights into the health of those industries and the broader economy.</p>