听力原文： A lot of people in the United States are coffee drinkers. Over the last few years, a trend has been developing to introduce premium specially blended coffees known as gourmet coffees into the America market. Boston seems to have been the birthplace of this trend. In fact major gourmet coffee merchants from other cities like Seattle and San Francisco, came to Boston where today they are engaged in a kind of coffee war with Boston's merchants. They are all competing for a significant share of the gourmet coffee market. Surprisingly the competition among these leading gourmet coffee businesses will not hurt any of them. Experts predict that the gourmet coffee market in the United States is growing and will continue to grow to the point that gourmet coffee will soon capture a half of what is now a 1.5 million-dollar market, Studies have shown that coffee drinkers who convert to gourmet coffee seldom go back to the regular brands found in supermarkets. As a result these brands will be the real losers in the gourmet coffee competition. What is the main topic of the story?