Wow! what kind of population are we talkin about?
I think the NGC database is updated each Monday, so this data point isn't in it yet. But, as of this moment at NGC, there are 56 of the 2001D G500Y graded: 29 are MS69 and 0 are MS70. Next week, after the database is updated, it should show "1" in MS70. PCGS has 16 graded 2001D G500Y: 11 in MS69 and 0 in MS70. So for a brief moment, at least, it is the only one in the world.