I think it's more a result of players experience and ratings rather than a factor. Player skills + matchup --> Ratings --> +/-
mmmm i dont think so.
Its the 'Efficiency' rating as far as i understand it.
Which, im 99% sure is the point differential for a player when he is on the court. As explained in posts above.
They use this in the NBA as a measure of a players influence on the game.
However, in NBA a backup PG will spend more time with starters/other good players, when compared to BB. (In my personal experience)
So a backup PG in NBA probably has a season average of +2.5 whilst someone like Derrick Rose has a +/- of + 21.88 (dunno who his backup is, but Ronnie Brewer came off the bench last year, and his +/- was 6.06)
In BB, i find most of my backups do sub in with other backups (which is just due to my lineup settigns).... but this does mean, that if you had a season +/- average, it would probably be in the negative for a backup. just cause they are so crap in comparison :)
In fact, on buzzer-manager, this stat is available. Its called 'Efficiency '
Please someone correct me if im babbling.