In sports, a closed league is a type of sports league where the number and identity of the teams taking part in the sports league activities does not change from year to year due to the performance of the member teams. A closed league is the opposite of leagues with promotion and relegation systems (often referred to as open leagues) where teams can be sent down to lower leagues if their performance is poor enough. Closed leagues are the most common form of sports leagues in North America and is also a common form of sports league in Australia and Singapore. Motorsport series such as Formula one have also been described as closed leagues. Closed leagues are sometimes considered a form of sport monopoly.