Illusion of Objectivity: PSA Grading Practices Examined

Spreadsheet of Data:

https://docs.google.com/spreadsheets/d/11kUSbkPQsHDT76qbDUsBvlwrelYRLA_jIJz9374j9IQ/edit?usp=sharing

This video explores PSA's grading practices for mint condition cards by comparing the ratio of 9's to 10's for a number of key cards between 1978-1993.

The 9:10 ratios of the key cards are compared to common cards in the same set to determine if PSA grades key cards with the same standards they use for all other cards. The 9:10 ratio can tell us which cards in a set are graded toughest by PSA. Those cards will have the highest 9:10 ratio in their set.

If PSA grades cards fairly and objectively across the board than there should be little/no difference in the 9:10 ratio's of the key cards and the commons. For example, we might see in the 1984 Donruss set that the Mattingly card is graded toughest, but in the 1985 Topps set a common card might be the toughest 10. We shouldn't see a pattern where one type of card is continually graded the toughest in set after set.

Another important measure paired with the 9:10 ratio is using Printing Sheet Comparisons. Printing sheets provide a wealth of knowledge to test PSA's practices because we can identify cards that are in a similar position on one or more printing sheets for that set. We can then compare these cards to see if there is some consistency between how PSA grades all cards in that set.

I encourage you to watch the whole video; it can be a complex issue, one that I tried my best to simplify.

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