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[World of Darkness] How many vampires are there? Like. In total? What are some interesting population statistics?

I'm curious how many Vampires there are in the contemporary World of Darkness. Are they in the hundreds? The Thousands? A few million? How large is a 'large' accumulation of vampires?

How many of these vampires are active? How many are ancients, methuselahs, and neonates? What's the average 'age' of the vampires?
gpt
The closest approximation is that there is about 1 vampire for 100 000 mortals. This of course includes only curently active vampires, not the ones that lie in torpor.

Realsitically, big cities might have much more dense vampire population, even 1/10 000, since blood is easier to come by, and population of vamps is harder to control.

So conservatively, we are talking about something between 60 000 to 80 000 active vampires, and probably around 10 000 in hibernation.

How many ancients? This nobody knows, but probably less than 100, and most of those are in torpor.
As for methuzelahs, probably a 1000-2000 or so. Ancillae, neonates and weak blooded scum make up the rest.
With each generation, vampire population rises more or less 2-3 times, but there were times of culling (example: the first war with Sabat), and great increases in population (late days of the Roman Empire, or today)

As for the average age, the numbers of vamps rose in the recent years so much that the average is probably below 50yo, including less than 30 years of being an actual vamp. 
So, if you were to meet a vampire, it would be most likely that it was alive longer than it was undead.
Also, its worth noting that each generation of vamps is shorter. Father Cain, 2nd generation and 3rd generation waited centuries before siring another generation. Further generations waited at least 100 years or so before making another one of their kind. Up to the late XIX century, we only reached, on average, 8-9 generation, and then in less than 100 years, we reached 15th generation. The youngest weakbloods wait less than a year before siring their own childe, and its only the impotency of their blood that prevents them from literally vampirizing the whole planet due to stupidity and exponential numbers.

(OWoD) By far the most numerous clan is Brujah, followed by Toreador and Gangrel. The number of Nosferatu is unknown, and the other main clans are fairly small by comparison.

Vampires also outnumber both werewolves and mages by a a significant margin, and are (as far as we know) the most numerous supernatural creatures in the World of Darkness.