Statistical confidence for each performance rating is based upon the number of organizations scoring the outsourcing service. Black Book identifies data confidence by one of several means:

Top-10-ranked vendors and advisors must have a minimum of five unique clients represented. Broad categories require a minimum of 20 unique client ballots. Data that are asterisked (*) represent a sample size below required limits and are intended to be used for tracking purposes only, not ranking purposes. Performance data for an asterisked vendor's services can vary widely until a larger sample size is achieved. The margin of error can be very large and the reader is responsible for considering the possible current and future variation (margin of error) in the Black Book performance score reported.

Vendors, associates, consultants and advisors with over 20 unique client votes are eligible for top 10 rankings and are assured to have highest confidence and lowest variation. Confidence increases as more organizations report on their outsourcing vendor. Data reported in this form are shown with a 95% confidence level (within a margin of 0.25, 0.20 or 0.15, respectively).

Raw numbers include the quantity of completed surveys and the number of unique organizations contributing the data for the survey pool of interest.