A monthly published statistic: of graded sports-card sales we audited, how many realized less than the same card would have brought raw, once the grading fee is counted — and how many dollars that destroyed. The basket of cards is defined by a third party's public most-graded lists, raw values are taken at the time of each sale, and the fee is a stated parameter with a sensitivity table.
The pattern the index measures is a cliff by grade: the top grade tends to pay, the next tends to break even, and grades below it usually sell for less than raw plus the fee. The first official month publishes after a full month of basket coverage.
Aggregates only — individual sale records are not redistributed. To price your own card before grading it, use the free grading calculator.