MAVS 108, PELS 92

[mavsluvr]

So the NBA has ONE statistic that they have tracked their entire existence: points scored. 

It is the only stat that the NBA makes its decisions on as it compares the points scored of each team every game and gives a win to the team that had the positive differential and a loss to the team that had the negative differential. The NBA has chosen to say that the team that scores more points than their opponent has won and therefore out-performed their opponent. So when I say how a team "performs" that's what I mean. It is the only performance the NBA cares about. NBA has never given a team a playoff spot for shooting a better percentage or having less turnovers, only for outscoring their opponent over the course of a certain number of games. 

Therefore +/- absolutely tells you how a team is "performing" in the only way the NBA actually cares about at the end of the day. Because +/- tells you if you have outscored your opponent or not: did you win or not. Last night the Mavs were +16 as a team, therefore the NBA gives them one of those treasured wins.

Maybe we are getting down to the ambiguities in the use of language. 

I understand you to be saying that, when you use the word "performance," what you really mean is "point differential." I believe the word "performance," as used by most sports analysts, covers a wide variety of aspects of play, generally adding up to whether the player executed well or poorly in the various elements comprising a game. 

I can assure you that point differential is not the only stat the league makes decisions on or cares about. The NBA awards the team scoring the most points a win, but does not purport to declare that the winner has outperformed the loser in any other respect. 

If you are indeed using performance to equal "point differential," then use of +/- as a measure is simply stating a truism. It then only means that whichever group has the highest point differential has scored more than their opponent for the segment in question. Therefore, it can never be "wrong," because all it is doing is defining itself. 

I do not think these terms mean what you think they mean.