My guess is around 60,000 Diamond members.

Completely anecdotal and based on nothing...

60 Million HHonors members apparently of late...likely 12 Million that are active (points activity in last year, using 20% principal), likely 6 Million that are staying twice in the last year (a Hilton definition of Diamond active accounts from the past instead of the points activity, a simple 50% of the active base gut feeling)...and therefore assuming the same roughly 1% top tier is desired...60k members at Diamond level.

Plenty of matched diamonds or 8 stay diamonds that then only used it to get benefits on an aspirational property for a week or two the following year so I have no issue with believing that there are plenty of members that are not active at diamond level but are diamonds...

In a quick search for further info (it's a slow day at work)...I came across a nugget that interested me...HHonor members accounted for over 50% of all room nights globally at Hilton group hotels in 2016.

60M and 50% room nights taken from this Hilton brochure:

http://hiltonworldwide.com/assets/pd...t_brochure.pdf

Caveat Emptor as always!