Posted By:
Joe ToccoI'm not familiar enough with the two issues say if it's viable, but the discrepancies in the population of T206 vs. T213 could be partially explained by submission bias. If a common T206 PSA 1 sells for $25 and a common T213 PSA 1 sells for $100, you'll see a higher percentage of all T213's submitted than T206's. Basically what I'm saying is, the pop reports are not necessarily indicative of the spectrum of grades existant in each respective set.
Other partial explanations include "finds," factory back-door sets (like the $800k Cracker Jack set), and storage bias (if T213s were traditionally thought to be junk, they may not have been protected as well as T206's). Also, resubmissions could be a factor. If the difference in price between a 1 and a 2 is $50, you won't see many 1's get resubmitted. But you'll see a lot of 5's get resubmitted in hopes of a $1000 value gain if it gets slabbed a 6. I have no doubt that resubmissions are more prevalent in more popular sets.
Of course, there are some alterations out there too 
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Joe