I've been bugging Doug, Scott, and Skype about the efficiency ratings and spent a few hours today investigating the formulas themselves. I found a few and am notating them here. These four formulas are tested and confirmed. Working on the others with the exception of PER.
AstR:
(Assists x 100) / [(Field Goal Attempts + (Free Throw Attempts * 0.44) + Assists + Turnovers]
ToR:
(Turnovers x 100) / [(Field Goal Attempts + (Free Throw Attempts * 0.44) + Assists + Turnovers]
ORR:
100 * Offensive Rebounds * (Team Min / 5) / Minutes Played * (Team Offensive Rebounds + Opponent Team Defensive Rebounds)
DRR:
100 * Defensive Rebounds * (Team Min / 5) / Minutes Played * (Team Defensive Rebounds + Opponent Team Offensive Rebounds)
RR:
100 * Rebounds * (Team Min / 5) / Minutes Played * (Team Total Rebounds + Opponent Team Total Rebounds)
Update: Here are some definitions of the rest. Copied some of it from ESPN.
Usg:
Usage percentage is an estimate of the percentage of team plays used by a player while he was on the floor.
(Formula uses League Pace which I am trying to confirm can just be an average of our Pace rankings in Team Leaders.)
PER:
John Hollinger's Rating. Player Efficiency Rating is the overall rating of a player's per-minute statistical production. The league average is 15.00 every season.
VA:
Value Added - the estimated number of points a player adds to a team’s season total above what a 'replacement player' (for instance, the 12th man on the roster) would produce. Value Added = ([Minutes * (PER - PRL)] / 67). PRL (Position Replacement Level) = 11.5 for power forwards, 11.0 for point guards, 10.6 for centers, 10.5 for shooting guards and small forwards
EWA:
Estimated Wins Added - Value Added divided by 30, giving the estimated number of wins a player adds to a team’s season total above what a 'replacement player' would produce.