T206 Total Population SGC vs PSA

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Posted By: cmoking

From the data that Jim and Al presented on this thread, here are the summaries of the two companies side by side.

I put the PSA 9Q into the PSA 7, PSA 8Q into PSA 6 and PSA 7Q into PSA 5.
I split the SGC 70s into half 5 and half 6. I split the SGC 86 int half 7 and half 8. I split the SGC 92 into half 8 and half 9. There was no particular reason why I converted SGC grades into the PSA system and not vice versa.

I'm sure there are a lot of theories about the grading differential. Is it a matter of one company giving out higher grades than the other? Or is it a matter of one company receiving higher quality cards to get graded than the other?

Grade PSA SGC Combined
1-2...14.6%..26.0%..17.3%
3-4...40.7%..51.2%..43.2%
5.....22.1%..16.1%..20.7%
6.....12.3%..4.2%...10.4%
7.....6.4%...1.9%...5.3%
8.....3.4%...0.5%...2.7%
9.....0.3%...0.1%...0.3%
10....0.0%...0.0%...0.0%


I couldn't get the numbers to format correctly, so I put in periods in between the numbers to try to get the formatting somewhat readable.