I ran a cross-player analysis of the top explorers or so against the explore
databases to identify areas/rooms that are no longer in the game. As a result
of this first analysis, I have positively identified and removed 428 of the
existing 17247 (2.48159%) rooms from the explore count. A bunch of you should
see your explore % increase a bit, as the divisor has been reduced. There may
be additional rooms to remove in the future, but these will require a rather
laborious and lengthy investigation to confirm and explore.

How does this happen, exactly?

Well, sometimes areas get recoded, removed, replaced, or moved, which may
still leave remnants of the old areas in the database.

Happy Exploring

-- Lord Tarken Aurelius, the Sage