Currently, the NFL has 32 teams, and the others have 30 each. The vast majority of major league teams are concentrated in the most populous metropolitan areas of the United States and Canada. Unlike the promotion and relegation systems used in sports leagues in various other regions around the world, those teams in the North American sports leagues remain static from season-to-season, unless they are disbanded or relocated. Each Big Four league, as well as Major League Soccer and the Canadian Football League, averages at least 15,000 fans in attendance per game as of 2013.