Association football is the world's most popular sport and is worth US$600 billion worldwide.[1] By the end of the 20th century it was played by over 250 million players in over 200 countries.[2][3][4][5][6] Around the world, the sport is played at a professional level by professional footballers, and millions of people regularly go to football stadiums to follow their favourite football teams,[1] while billions more watch the sport on television or on the internet.[7] Football has the highest global television audience in sport.[8] The sport had amateur origins and evolved into the modern professional competition.
^Guttman, Allen (1993). "The Diffusion of Sports and the Problem of Cultural Imperialism". In Eric Dunning; Joseph A. Maguire; Robert E. Pearton (eds.). The Sports Process: A Comparative and Developmental Approach. Champaign: Human Kinetics. p. 129. ISBN0-88011-624-2. the game is complex enough not to be invented independently by many preliterate cultures and yet simple enough to become the world's most popular team sport
^Mueller, Frederick; Cantu, Robert; Van Camp, Steven (1996). "Team Sports". Catastrophic Injuries in High School and College Sports. Champaign: Human Kinetics. p. 57. ISBN0-87322-674-7. Soccer is the most popular sport in the world and is an industry worth over US$400 billion world wide. 80% of this is generated in Europe, though its popularity is growing in the United States. It has been estimated that there were 22 million soccer players in the world in the early 1980s, and that number is increasing. In the United States soccer is now a major sport at both the high school and college levels