I've got a great example of why we need to use both NGC & PCGS population census numbers to assign values and Registry set scores.
I have a 1963 Half Dollar that is currently residing in a PCGS holder, and is graded by that company at MS66. The PCGS population at that grade level is 14 with none higher. However, the NGC population at that grade level is 64 with none higher. There are obviously more NGC coins than there are PCGS coins in this particular instance. I would think that the PCGS coins might deserve a little higher score than the NGC coins based solely on the population or current rarity.
I know that this topic could generate a big pile of contraversy, but wouldn't it be nice if someone could get this whole thing to work smoothly?