HuskerGeek's ViPR ratings are point ratings based on a calculation of each teams per set scoring efficiency. Each team's ability to score points and their corresponding propensity to give away points is iteratively compared against their opponents and the team's rating is adjusted.

WPA or Win Probability Added is calculated using play-by-play for each game and adding the changes in set win probability to the players participating.

If some of the ratings are missing, the database is probably being updated. They should be available within a couple minutes.