Fred Michel is one of 7.2 million Americans who moonlight.  Once a week, after his day job as medical director of a mental health center, the 40-year-old psychiatrist  heads to a part-time job at a treatment center for young people. Twice a month, he travels three hours to another teenage treatment center.   Last year, 5.4 percent of the American workforce held second jobs, according to the US Labor Department, and that looks set  to increase this year.   Many workers like the safety that moonlighting provides, says Carl Hausamn, the writer of "Moonlighting: 148 Great Ways to Make Money to the Side".  The information from the US Labor Department shows that 40 percent of US moonlighters in 1997 took a second job to meet household  expenses or pay off debts. Others save money or buy some special things.  People also take second jobs with an eye to the future--wanting to try out a new field or gain experience.  Michel started moonlighting when medical systems were unstable . He wanted to make sure he wasn't tied to one system that ended up failing.  Just as the purposes for moonlighting are different, the moonlighters cross all age and racial groups. And they work in a variety of industries---no longer just service,office and sales jobs.  As its name means, moonlighting still occurs mostly at night. And that results in some pressures. Chief among them is time. Full-time employers could misunderstand, too. Some companies do not allow after-hour work because they fear it will affect their employees' 9-to-5 performance. "The primary employer is saying, 'Wait, I'm paying you for the sharp, fresh, energetic you,'" says Tom Gimbel, president and founder of LaSalle Staffing in Chicago. "If you're burning yourself at both ends, it's going to show." Still, the good done to the moonlighters can be great. Besides extra income, moonlighters enjoy variety , freedom and chance to do something new. They also may find their part-time jobs strengthen what they do full time.  Besides, "it's fun," Michel says. Not only do his part-time jobs offer a chance to network, stretch his professional skills and make more money, but they also give him the variety he wouldn't find just in a full-time job. " _  ," he says, "and offering a little variety throughout the day." What is the article mainly about?
The reasons for moonlighting. The ways of moonlighting. The problems with moonlighting. The kinds of people who moonlight.