If you ask any trader or investor what is the most important currency to follow they would probably say the U.S. Dollar. After all, the U.S. Dollar is the world's reserve currency. If someone in Asia, or Africa wanted to buy a barrel of oil they would need to convert their money into U.S. Dollars in order to pay for that barrel of oil. Almost every major commodity is traded in U.S. Dollars, so it is understandable why the U.S. Dollar should be followed. If a trader or investor trades the U.S. Dollar Index, they are trading the U.S. Dollar verse a basket of six other major currencies, including the British Pound, Euro, and the Japanese Yen.