NBA Efficiency, invented by Martin Manley, is being considered the first ever player evaluation metric which indicates player’s linear efficiency.
NBA Efficiency does a nice job of explaining free agent salary. NBA Efficiency tells us about perceptions of performance. It just has some problems if our objective is to measure the impact a player has on wins.
All stat categories are weighted the same. Also, these ratings are not adjusted for game pace. Thus they do not have the precision of possession based stats.