are allowed. The most widely known system of ranking players is the Elo rating system, which is used for Chess and Go. Every player in the Elo rating system receives a rating based on his or her win–loss record, which establishes his or her position (or level) on the game ladder. Numerous efforts have been made to design better game ladders by analyzing the statistical correlation between relative ladder levels and a player's expected performance. A game ladder may be used as the ranking system itself, in lieu of a ranking system like Elo. In this case, players are moved up and down the ladder according to competitive results, dictated by previously determined rules. A unique game ladder system is the Masterpoints rating system used for contract bridge by the American Contract Bridge League. The Masterpoints system, unlike the Elo rating system, emphasizes participation (i.e., experience in terms of number of games played) over demonstration of skill. The Ultimate Fighting Championship considers its official rankings (decided by a media pool, based on match results) when matchmaking, though not strictly. Due to the high incidence of training injuries, unranked or low-ranked replacement fighters often compete higher up the ladder than they otherwise would. This is also (more rarely, usually on pay-per-view) done for promotional reasons, when a big name or rivalry makes a low-ranked fighter the more marketable option. Sometimes no similarly-ranked opponents are available, and a fighter may risk losing their spot to a low-ranked one just to stay busy. Winners are interviewed after fights, and all fighters are required to use Twitter. Challenges through these avenues (and others) are encouraged. Though not binding, a publicly agreed fight usually occurs as soon as practical. Rematches are generally disallowed, excepting some championship bouts and others ending in controversial decisions. The Korea Baseball Organization has the fourth-seeded team play host to the fifth seed, with the winner playing the third seed. The second-seeded team plays the winner of that game, and whoever wins advances to play the top-seeded team in the Korean Series.Similar systems are used in multiple League of Legends leagues' playoffs and regional finals,which are called "King of the hills",which could prevent match fixing. References Bibliography Further reading Rating systems de:Ladder