听力原文： Do you like getting a piece of hand-written mail? Are there people whose letters you've saved for years7 The art of letter writing seems to be dying for many people as more and more of us are turning to our computers to send a quick email. You might think the United States is a country of serious internet users, but there are many people whose only on-line activity is sending and receiving email. In 1999, Americans sent 2.2 billion email messages compared to 293 million pieces of first class mail. People have become more and more dependent on email for quick communication. In addition to the quick communication that email gives us, many people are using instant messages to communicate. How does this work? First you make a list of your on-line friends. When you go on-line, your computer tells you if the people whose names are on the list are on-line too. If they are, you can send them an instant message and have a real time chat. Teenagers especially love sending and receiving instant messages and they love going to chat rooms to talk to their internet friends. But when people send email and instant messages, they often don't give much thought to how they write. Many people use short forms and omit capital letters. They simply write the first thing that comes into their head, click and send it. Even though people are writing more, their writing is usually not something to keep and read again years later. How many email messages did Americans send in 1999?