In professional sports, a salary cap (or wage cap) is an agreement or rule that places a limit on the amount of money that a team can spend on players' salaries. It exists as a per-player limit or a total limit for the team's roster, or both. Several sports leagues have implemented salary caps (mostly closed leagues), using them to keep overall costs down, and also to maintain a competitive balance by restricting richer clubs from entrenching dominance by signing many more top players than their rivals. Salary caps can be a major issue in negotiations between league management and players' unions because they limit players' and teams' ability to negotiate higher salaries even if a team is operating at significant profits, and have been the focal point of several strikes by players and lockouts by owners and administrators.[1][2]