Yoga pants are form-fitting trousers designed for yoga as exercise and first sold in 1998 by Lululemon, a company founded for that purpose. They were initially made of a mix of nylon and Lycra; more specialised fabrics have been introduced to provide moisture-wicking, compression, and odour reduction. The market has increased both through the popularity of yoga and because many women wear yoga pants as casual everyday dress. This is part of a long-term "athleisure" trend of increasing informality in dress, threatening sales of traditional jeans. The use of yoga pants for more formal and office wear has been criticised by Karl Lagerfeld and others. In the United States, the wearing of yoga pants other than for exercise has aroused controversy, both for school use and when worn by women. Global sales of yoga clothing have all the same grown rapidly, reaching some $31 billion by 2018.