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In American and Canadian football, a two-point conversion or two-point convert is a play a team attempts instead of kicking a one-point conversion immediately after it scores a touchdown. In a two-point conversion attempt, the team that just scored must run a play from close to the opponent's goal line (5-yard line in amateur Canadian, 3-yard line in professional Canadian, 3-yard line in amateur American, 2-yard line in professional American) and advance the ball across the goal line in the same manner as if they were scoring a touchdown. If the team succeeds, it earns two additional points on top of the six points for the touchdown. If the team fails, no additional points are scored. In either case, the team proceeds to a kickoff. Various sources estimate the success rate of a two-point conversion to be between 40% and 55%, significantly lower than that of the extra point, though if the higher value is to be believed, a higher expected value is achieved through the two-point conversion than the extra point. ==Adoption of rule== The two-point conversion rule has been used in college football since 1958〔''Time'' "(The Two-Point Conversion, )", October 6, 1958.〕 and more recently in Canadian amateur football and the Canadian Football League (1975).〔(【引用サイトリンク】url=http://www.cfl.ca/page/his_timeline_1970 )〕 In overtime situations in college football, the two-point conversion is the mandatory method of scoring after a touchdown beginning with the third overtime. The American Football League used the two-point conversion during its ten seasons from 1960 to 1969. After the NFL merged with the AFL, the rule did not immediately carry over to the merged league, though they experimented in 1968 with a compromise rule (see below). The NFL adopted the two-point conversion rule in 1994.〔WiseGeek.com () Definition.〕 Tom Tupa scored the first two-point conversion in NFL history, running in a faked extra point attempt for the Cleveland Browns in a game against the Cincinnati Bengals in the first week of the 1994 season. He scored a total of three such conversions that season, earning him the nickname "Two Point Tupa". The NFL's developmental league, NFL Europe (and its former entity, the World League of American Football), adopted the two-point conversion rule for its entire existence from 1991 through 2007. Six-man football reverses the extra point and the two-point conversion: because there is no offensive line in that league, making kick protection more difficult, plays from scrimmage are worth one point but successful kicks are worth two. It is also reversed in many high school football and youth football leagues, since there are not often skilled kickers at that level. A variant of this, especially at the youth level, is to allow one point for a running conversion, two points for a passing conversion, and two points for a successful kick. The Arena Football League has recognized the two-point conversion for its entire existence (in both its original 1987–2008 incarnation and its ongoing revival), allowing for either a play from scrimmage or a drop kick to be worth two points. (The additional extra point for a drop kick is unique to arena football.) In 1968, leading up to the AFL-NFL merger, the leagues developed a radical "compromise" rule that would reconcile the fact that the NFL did not recognize the two-point conversion but the AFL did: the relatively easy extra point kick would be eliminated and only a play from scrimmage would score one point. The rule would be used for the interleague matchups for that preseason, and would not be tried again. Both the World Football League and the XFL revived this concept, making it a point not to institute a two-point conversion rule so as to eliminate the easy kick. What would constitute a two-point conversion in other leagues only counted one point in the AFL-NFL games, WFL, or XFL. However, the XFL later added a rule in the playoffs that allowed the scoring team to score two (or even three) points by successfully executing a play from a point farther from the opponent's end zone (two points if the team could score from the five-yard line and three points if they could score from the ten-yard line). As of the summer of 2014, the conversion by place kick is under review by the NFL. This new format would award seven points for a touchdown without an extra point attempt, eight points with a successful conversion by running or passing, and six points with an unsuccessful extra point attempt. This new format is proposed because of the almost certain probability of making a conversion by place kick (1,260 out of 1,265 for the 2013 season).〔(【引用サイトリンク】url=http://profootballtalk.nbcsports.com/2014/01/20/roger-goodell-nfl-will-explore-eliminating-the-extra-point/ )〕 This proposal was never considered at the league owners' meeting in spring 2014; instead, the league used the first two weeks of its preseason for an experiment that moved extra point attempts back to the 20-yard line with the condition that if a team opted to attempt a two-point conversion instead, the line of scrimmage on the try would remain at the 2-yard line. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Two-point conversion」の詳細全文を読む スポンサード リンク
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