ADJUSTED +/— PLAYER RATINGS
Basketball is a team game. The definition of a good player is somebody who makes his team better, not a player who scores 40 points per game. My favorite story about what defines a good player is told by Terry Pluto in his excellent book Tall Tales.1 The late great Celtics coach Red Auerbach said that whenever the Celtics practiced, KC Jones's team always won. This must mean he was a good or great player. Yet during his peak years his PER rating was around 10, indicating he was a poor player. KC must have done some great things that did not show up in the box score.
The first statistic that tied a player rating to team performance was hockey's + /— statistic. A player's + /— statistic is simply how many goals a player's team outscores their opponents by when the player is on the ice (power plays, when one team has more players on the ice, are excluded from the calculation). Since 1968 the NHL has kept track of + /— for each player. The highest recorded + /— was that of Bobby Orr, who during the 1967–68 season earned a + 124 goal + /— .
For NBA players, Pure + /— per 48 minutes on court was thought to be a valid measure of how a player helped his team.2 The problem with Pure + /— statistics is that a player's Pure + /— statistic depends on the quality of the players he plays with and against. Suppose Player A had a Pure + /— of 0 and played for the 2006–7 Memphis Grizzlies, the league's worst team.
1 Terry Pluto, Tall Tales: The Glory Years of the NBA (Bison Books, 2000).
2Since 2003 + /— statistics have been available 2003 at http://www.82games.com, and be-
ginning with the 2006–7 season, Pure + /— statistics have been available on http://www.nba
.com (http://www.nba.com/statistics/lenovo/lenovo.jsp). As of November 2007, nba.com
posts each player's individual + /— updated while the game is being played.