Five years ago, David Smith wore an expensive suit to work every day. “I was a clothes addict(迷),” he jokes. “I used to carry a fresh suit to work with me so I could change if my clothes got wrinkled(皱的).” Today David wears casual clothes — khaki pants and a sports shirt — to the office. He hardly ever wears a necktie. “I’m working harder than ever,” David says, “and I need to feel comfortable.” More and more companies are allowing their office workers to wear casual clothes to work. In the United States, the changes from formal to casual office wear have been slow. In the early 1990s, many companies allowed their workers to wear casual clothes on Friday (but only on Friday).This became known as “dress-down Friday” or “casual Friday”. “What started out as an extra one-day-a-week benefit for workers has really become an everyday thing,” said business adviser Maisly Jones. Why have so many companies started allowing their workers to wear casual clothes? One reason is that it's easier for a company to attract new workers if it has a casual dress code. “A lot of young people don't want to dress up for work,” says the owner of a software company, “so it's hard to hire people if you have a conservative dress code.” Another reason is that people seem happier and more productive when they are wearing comfortable clothes. In a study made by Levi Strauss and Company, 85 percent of employers said that casual dress has a side effect on work. Supporters of casual office wear also say that a casual dress code helps them save money. “Suits are expensive, if you have to wear one every day,” one person said. “For the same amount of money, you can buy a lot more casual clothes.”According to this passage, which of the following is TRUE?