The global hotel industry generates approximately between 400 and 500 billion U.S. dollars in revenue each year, one third of that revenue is attributable to the United States. Some of the biggest hotel chains (groups) are the InterContinental Hotels Group, Marriott International, Hilton Worldwide, Accor, STARWOOD HOTELS & Resorts, and the Wyndham Hotel Group. Three of the most important hotel performance indicators are the Average Daily Rate (ADR), the revenue per available room (RevPar), and the occupancy rate.