Plus−minus is a sports statistic used to measure a player's impact on the game, represented by the difference between their team's total scoring versus their opponent's when the player is in the game. In ice hockey, it measures a player's goal differential. When an even-strengthgoal or shorthanded goal is scored, the plus–minus statistic is increased by one for those players on the ice for the team scoring the goal; the plus–minus statistic is decreased by one for those players on the ice for the team allowing the goal. Power play or penalty shot goals are excluded. An empty net does not matter for the calculation of plus–minus. The statistic is sometimes called the plus−minus rating. A player's plus−minus statistic is calculated for each game played, to provide a more meaningful measure over a full season. The statistic is directly affected by overall team performance, influenced by both the offensive and defensive performance of the team as a whole.
History
The NHL's Montreal Canadiens were the first team to track the plus−minus of its players, starting sometime in the 1950s. Other teams followed in the early 1960s, and the NHL started officially compiling the statistic for the season. While Emile Francis is often credited with devising the system, he only popularized and adapted the system in use by the Canadiens.
Only four players have been multiple single-season leaders for the plus−minus statistic: defenseman Bobby Orr led the leaguesix times, Wayne Gretzky led the league four times, while John LeClair and Chris Pronger were two-time leaders. One player on the career top five list, Ray Bourque, was never a single-season leader, while all-time career leader Larry Robinson only set the single-season mark once. Two players on the season top five list, defensemen Bobby Orr and Dallas Smith, achieved their high mark playing as a defense tandem on the same Boston Bruins team. Since the NHL started tracking the plus−minus statistic in the season, the top achievements have been: Top 5: Season high
There are some drawbacks to the traditional calculation of the plus–minus statistic in ice hockey. Not all types of goals are included, specifically power play goals. Every goal included in the calculation is weighted the same regardless of the situation - even strength, power play, short-handed or empty net. Also, traditional plus–minus is not applied to goaltenders. Situational plus–minus is an alternative calculation that takes into account all types of "team-based" goals, which excludes only penalty shot and shootout goals. Each goal is weighted based on the number of skaters on the ice. The plus–minus rating is calculated by dividing the number of skaters on the ice for the team scored upon by the number of skaters on the ice for the scoring team, applied as a plus to all players on the ice for the scoring team and as a minus for all players on the ice for the team scored upon. The situational plus−minus statistic has recalculated the NHL plus–minus statistic going back to the 2008-09 season, for which the top achievements have been: NHL Top 5: Season high
Although the statistic was pioneered in the sport of hockey, it has found its way into use in other sports and areas of life. For instance, the NBA'sHouston Rockets first utilized a modified version of the stat, which helped reveal the unheralded effectiveness of light-scoring Shane Battier. It is now in regular use throughout the NBA.
