Ice hockey is a sport that is contested at the Winter Olympic Games. A men's ice hockey tournament has been held every Winter Olympics ; an ice hockey tournament was also held at the 1920 Summer Olympics. From 1920 to 1968, the Olympics also acted as the Ice Hockey World Championships, and the two events occurred concurrently. From 1920 until 1984, only amateur athletes were allowed to compete in the tournament, and players from the National Hockey League (NHL) were not allowed to compete. The countries that benefited most were the Soviet Bloc countries of Eastern Europe, where top athletes were state-sponsored while retaining their status as amateurs. In 1970, after a disagreement over the definition of amateur players, Canada withdrew from the tournament and did not send a team to the 1972 or 1976 Winter Olympics. In 1986, the International Olympic Committee (IOC) decided to allow professional athletes to compete in the Olympics, and starting in 1998, the NHL began accommodating a break in its schedule so that the players can participate at the Winter Olympics. Women's ice hockey was added to the program in 1992 and the first tournament was held at the 1998 Winter Olympics. Both events have been held at every Olympic Games since.