Something ive been trying to work out and calculate without just vague assumptions are essentially:
Question 1 - With the population of PSA 10s on a specific card - these typically indicate the difficulty to grade a card when compared to the rest of the PSA grades, however is there anyway to tell whether the card itself was originally fairly difficult to grade, but as its values shot up, there is a flurry of submissions for sub par grades just to get the card graded thus making its psa 10 pop look even more desirable (T17 is probably a good example moving forwards). This then makes the PSA 10s look much rarer then other PSA 10 cards that simply arent graded because people arent interested to do so…tons of holos have pops of psa 10 less then 20 but we know its not due to gradeability.
Question 2 - Do we always assume holos in sets have the exact same pull rates if they are the same type of holo rarity, and any difference in PSA pop is purely down to the collectors desire to grade the card? I know Charizard Unlimited is a good example of this with it obviously being a card many want to grade…but further to this point, can we assume that a more desirable card will remain higher pop over time then those that dont because they have been thrown away/not looked after etc. I.e I feel as though, other then theme deck variants, theres more chance a charizard unlimited acheving a psa 10 then say a psa 10 Nidoking/Raichu/Ninetales because over time the card would of had a higher chance of it sitting in a binder then the others.
Seems like you have about the correct thought process in everything you said. I’m sure the unpopular Pokemon get graded much less. For example yes Yanma is hard to grade but do you really think people sent off their Yanma cards originally before price went up. I’m sure some that would have got 10s got smashed in a binder or lost who knows. But this is a perfect example it’s a bug Pokemon and not even a kool one like Scizor or Scyther or even Pinsir
It’s a safe assumption that all the holos of a particular set have roughly the same pull rate.
If you want to know how hard a card is to grade in a PSA 10, one way to do it is to look at how many PSA 10s have been graded relative to the total number of PSA submissions. But this won’t be a perfect measure - there are a couple of other factors that should be taken into account.
—> One factor to consider is that people are more likely to submit cards they perceive as being more valuable - for example, people will submit almost any 1st ed Base Charizard to PSA but people probably won’t bother submitting 1st edition Jungle Oddish unless they think it has a damn good chance of getting a PSA 10.
—> Another thing to take into account is that very valuable cards are more likely to be re-graded which might inflate the population for certain grades likes PSA 9s and PSA 8s.
There’s no perfect science for figuring out if PSA 10 populations between cards will remain in proportion. Consider for example the case of Neo Destiny Shinings and Holos. For a long time, many people probably only bothered getting the Shinings from this set graded. But now the holos from this set are also worth a lot of money. Over time I would expect the proportion of Neo Destiny holos to Neo Destiny Shinings to change. Years ago, the same thing was true with 1st edition Base Set Charizard - it had a much higher PSA 10 population than any other Base Set holo because some people would only submit this card. But over time, the Zapdos and the Venusaur actually surpassed Charizard in the PSA 10 pop.
Remember that PSA pops don’t necessarily reflect a card’s true population. To use 1st ed Base as an example yet again, the holos in this set have a long history of being graded compared to other set cards. Even when it comes to the non-holos in the same set, many of these cards used to have a lower population than the holos in the set, but things changed once more people recognized the value in grading the non-holos. You can probably apply the same logic to other sets that have more recently started increasing in value.
We know that holos have the same pull rate because there are still some uncut sheets floating around. I know I’ve seen one for 1st Base at the very least but I know there are others. The way the cards are distributed on the sheet indicates equal probabilities and even if there isn’t one for a given set it’s pretty safe to assume they didn’t change it. Even today (Nintendo/TPCI vs Wizards back then) in the era of better brand awareness I’ve seen a sheet of full arts and the incredibly desirable Mewtwo EX (Next Destinies) is there the same number of times as Regigigas and the other ones that weren’t as hyped. The printing pattern is the same.
Moreover, you would probably be able to tell if there was some sort of distribution bias in the foil cards. The example I’ll use is EX Dragon, in which the TV Reporter card (the last numbered card in the set I believe) was left off many of the reverse holo sheets. People quickly realized that nobody had that card and now it is considered one of the rarest English set cards. In large quantities a small shift of the distribution would become apparent pretty quickly I think.