Tourism is the principal economic activity. Saipan and Rota are the main tourist centres and offer luxury hotels. The tourists are mainly Japanese and Americans. Subsistence farming, including the cultivation of taro, cassava, yams, breadfruit, vegetables, and bananas, is practiced extensively by many islanders to supplement their cash income. Investors from Korea, China, and the Philippines have expanded the islands’ production of clothing and accessories, making the garment industry a major component of the Northern Marianas economy. The investors are attracted by duty-free and quota-free access to the U.S. mainland.