How large could a population of supernatural beings be and still be plausibly hidden?

Question

I am trying to figure out how large the population of supernatural beings can be in a stereotypical urban fantasy setting before their numbers stretch the suspension of disbelief. I.e., your standard setting where supernatural beings live among humans under some sort of masquerade system.

Figuring out how big your supernatural society can be is obviously important for plot purposes. Make the supernatural population too large (say, 1 in 25), and it becomes ridiculous that the supernatural could be kept secret because everyone would know at least someone who is supernatural. Make it too small (say, 100 people worldwide) and you dramatically restrict the possibility for narrative conflict because you have at most one vampire/werewolf/whatever per large city.

The World of Darkness gives an oft-cited statistic that there is about 1 vampire for ever 100,000 humans. The best I could figure for a reasonable estimate would be a population ratio comparable to the prevalence rate for a rare disease: something rare enough that almost no one knows someone personally that fits the criterion, even though the disease itself is real.

I realize that in reality there is probably no way the supernatural could keep a reliable masquerade from humanity for any length of time. There have been studies that suggest even the best-kept conspiracy (which would be analogous to, in this case: insta-fail if any evidence of supernaturals got out, complete unity by the supernaturals in wanting to stay hidden, and no supernatural-hunting organization of muggles that want to expose them, all of which is highly unlikely) could only last a few decades at best. Even in these situations the best-kept secrets would be at best like the mafia: everyone knows the mafia exists, but few people know who the individual members of the mafia are or their rank within the organization. I am more looking for an estimate of the largest population possible that would not also break the reader's suspension of disbelief because there is no way a subpopulation of that size could be completely unknown to society at large.

Additional Parameters:

• The supernatural beings have both a distinctly inhuman form (or cover-blowing superpowers) and can also pass for human to most people. Think your standard urban fantasy vampires, werewolves, wizards, faeries, djinn, etc. Or even better, the Wesen from Grimm. So it's not a case of "they can pass for human even when using supernatural abilities".
• The supernatural beings in question do not feed on humans. Therefore, their population is not constrained by the availability of prey, like it would for something like vampires.
• Similarly, because they can reproduce with humans or can reproduce non-sexually (i.e., vampire or werewolf bites) inbreeding or difficulty in finding mates to continue the species is not a concern
• There are no "secret hidden cities" or "town where everyone is supernatural but they pretend to be normal to outsiders" that the supernaturals can set up in the boonies, they are intermixed with the human population.
• For the purposes of this question, it only matters that the general public be unaware of the existence of the supernatural. Muggle Best Friends or family members are allowed to know, the existence of the supernatural just can't be common knowledge. The government is also allowed to be aware of supernaturals and complicit in aiding the masquerade. Obviously if the government did know about supernaturals and was abetting in hiding their existence, it is only a matter of time before government corruption/incompetence/international realpolitik or WikiLeaks spills the beans to everyone, but still. If you want to go ahead and give separate estimates for population sizes if the government is abetting the masquerade (and hence can make evidence disappear) be my guest, but you don't have to.
• No mind whammies, glamours, or flashy thingies to make people forget about the supernatural. If muggles see evidence of the supernatural, the only way the supernaturals have to make the evidence disappear through begging, bribery, vandalism, or threats/murder.
• There is no magical "weirdness censor" that will make humans just plain refuse to believe in the supernatural to the point of active denial. The ability of humans to disbelieve the supernatural is about the same as it is in real life. An isolated paranormal event will be written off. A single person spouting nonsense will be seen as crazy. Repeated sightings of a creature in the woods will draw in cryptid enthusiasts. But strong enough evidence that can't be dismissed by a dedicated skeptic won't be ignored and people will notice when things are going on, even if they can't peg it as supernatural. What constitutes failure in this scenario is the supernatural being treated as "real" and common knowledge by your average person, rather than just an urban legend.
• The majority of the supernatural community wants to maintain the masquerade. Individual exceptions that believe the masquerade is oppressive exist, but they're a small number and are mostly taken out by internal self-policing by the supernaturals (read: staked in a dark alleyway). The supernatural community is mostly unified on this issue.

Answer 1

"There are no 'secret hidden cities' or 'town where everyone is supernatural but they pretend to be normal to outsiders' that the supernaturals can set up in the boonies, they are intermixed with the human population."

I think you might want to re-evaluate this restriction, since it has an extremely large impact on how your supernatural population develops and thus how large could be reasonable. It also affects the potential quality of life of your supernaturals in a very large way.

If your supernatural people reproduce in some controlled/intentional fashion and they all want to remain hidden, then it's natural that they will come together to form communities where everyone is "in the know". Both because it's much easier to keep things hidden collectively, and because if they're anything like baseline humanity in terms of social desires, then they'll naturally want to build a community and culture with other supernaturals.

This might not wind up as an entire "hidden city", but a smaller town in a less densely-populated area certainly seems plausible, or a particular neighborhood in a larger city. We certainly see this in the real world, where many cities have neighborhoods with large immigrant populations from the same part of the world -- think of how many cities around the world have a "Chinatown", as one example. Or as a closer parallel, many cities also have neighborhoods that are centers of their local LGBTQ populations.

If you allow for this sort of community-building, that not only lets much larger populations arise, but also allows for more relaxed use of their supernatural abilities within that community. If your three-year-old tries out their new wings by flying out the front door and doing loops in the front yard, it's not nearly as big a problem if your neighbor flies off after them instead of plastering videos all over their Instagram account.

Also, if the government is assisting in the masquerade, that would encourage the formation of supernatural communities or enclaves. Living in an all-supernatural community might even be mandatory, with varying levels of coercion involved depending on the government.

On the other hand, if your supernaturals arise spontaneously--at birth or via random chance later in life--that pushes the likelihood of discovery much higher, and thus the possible population that could remain hidden much lower. Especially in modern-day society, even a relatively small number of slip-ups can become well-publicized, and thus the possible usage of supernatural abilities is very curtailed. Every single supernatural that manifests becomes another possibility for word to get out. What if a world leader takes werewolf form for the first time in front of a giant crowd during a live, nationwide broadcast? What if the latest media darling's baby is born with blue skin and dragonfly wings? Could these be covered up? Sure, but only so well.

And if they are randomly-scattered like that, it becomes much harder for them to find and form any sort of community or shared culture, and thus it's more likely that some supernaturals might ignore or deliberately breach the masquerade before their fellows could intervene.

In the community scenario, I could imagine hundreds or even thousands of supernaturals within a single mid-size city--even if the overall prevalence within the general population is small, they'd be concentrated in specific areas. In the scattered-individual scenario, I'd be surprised if more than a few thousand could exist worldwide before someone managed to breach the masquerade in dramatic enough fashion, whether deliberately or mischance. There might not be more than a few hundred even in major countries.

Really, it all depends on the story you want to tell. If you want to tell a story where supernaturals live their lives in a normal-if-supernaturally-enhanced fashion, either separate from the general population or within it but still interacting with other supernaturals on a regular basis (like a certain series of Wizard School books), then let them form their own separate communities. If you want oppressed loners trying to eke out some connection to others of their kind while constantly on guard against discovery (A certain mutant-focused comic book franchise comes to mind), then keep them scattered.

Answer 2

This is actually a very interesting question! As I am writing a story which also includes this same type of super powered population, I think I might have some advice

Firstly, let's actually look back into history. These dreams of having powers and supernatural abilities are actually as old as humanity itself. With witches in the Medieval ages, to Gods, tales about miracles, and all of these supernatural legends told throughout generations. In real life of course, we know these aren't real. In a fictional world, people also think just like us: they think it's not real, that they're just legends. But what if in this fictional world, these events were actually real? What I mean by this is that it's impossible for an entire population to completely hide their nature. There obviously are going to be several people leaking the secret. Yet, if throughout history humans still don't think they exist, then that means that they were able to maintain the secret.

The human psychology

The human psychology is quite a complex thing, and it's pretty clear that people are afraid of the unknown. And if people do see supernaturals use their powers, no one would believe them; they would be called crazy, heretics, or attention-seekers. However, if government officials come across such powers, things might get tough for the supernaturals. However, I don't think the government would deliberately tell the public about supernaturals, as it would cause panic, and so this information might be classified. However, this still isn't good for supernaturals, they could be experimented on in labs for example, or taken away by the government for unknown reasons. Another problem would be if a supernatural uses their powers in public, with enough witnesses to make it believable. This is probably the worse case scenario, since both the people and the government would know.

Average Population

Take for example New York City, with around 8 million inhabitants. I think a good number of supernaturals in that city would be about 100 supernaturals. Now take that, and compare it to other big cities, who would also have about 100 supernaturals in them. Of course, some small villages might have one or two supernaturals in them, or maybe none at all, depending on the size of that village. Supernaturals are rare, but there are more than people think.

Hiding from humans

If realistically most supernaturals wanted to hide their powers effectively, it would be better for them to live in small villages, where there aren't enough witnesses to make a sighting go viral. I think that in order to hide their powers, supernaturals wouldn't really be able to have the most normal of lives. Maybe getting a simple job would be better than being a celebrity, since there are less risks of getting discovered. Children should not be sent to school until they can effectively hide their powers - or not even be sent to school at all, but be home schooled instead. For marriage, it would be a lot safer for supernaturals to stay together and not mix with the humans, even if they can reproduce. If it means hiding their powers at all costs, these are probably the best safety measures.

Answer 3

The limit is less about how many people can keep a Masquerade that they want to keep, but about at what point is there enough people to create an organized resistance to the cover-up that will ultimately succeed.

The Masquerade Itself

The key thing about this Masquerade is that its primary tenet is essentially security through obscurity. As the supernatural entities in the world can do just fine without humans, they can choose where they want to exist on the slider of isolation versus integration personally.

So the first main thing to decide is WHY there needs to be a Masquerade in the first place -- I didn't see a reason in the question. There needs to be a motive for the dwarfs, vampires, and fey to want to stay generally hidden from the world at large. It might be an outdated reason, but it needs to exist. Without a reason to hide, most people will not bother, and the veil will be lifted.

Next is how to deal with myth and legend. In our world, we already "know" that werewolves and vampires exist -- we have them in stories. We have tales of trickster fey, and angels and demons. Spirits of the world in various forms also pepper literature from ancient times. We already know, but I bet that most of us do not go looking for it and that is the key -- to keep people from wanting to look for it.

Also needing explaining is why your supernatural creatures wouldn't gravitate towards each other. Humans do it all the time -- we call them cities and towns. So is there any reason why after a few decades of codewords and conspiracies, there wouldn't be a Supernatural Quarter in a city or a town with a prominent werewolf population? Not that it is advertised as such of course -- that would be a disaster, but a neighbourhood with a higher population of X is certainly handy when a parent needs a sitter for a youngster without full control.

Basing it on today's world, Social Media and superpowered conflicts will be the biggest threats most likely since the former only takes enough slips for many to put it together starting a cascading failure of the whole thing, and the widespread presence of CCTV means that it will be difficult to hide an epic fight once the human guises come off. That and certain injuries from beings will be distinctive, as would the weapons needed to kill them. Bullets are not often made from or with silver or cold iron.

Your World

What kind of story are you telling in your world? If you have factions at each other's throat in a secret war that kills many, then that is going to drive that threshold population down as opposed to a story of beings that just want to live their lives and happen to turn into a implacable furry hound when the reflective orb reaches maximum visibility. Governmental assistance might allow this number to be higher as they have more power to arrange things to the being's benefits without tipping off the public. The trick is to not have a Ministry of Supernatural Affairs, but still work with them to make sure they fit in the frameworks of the laws.

I will toss a base number of 0.01% to 0.1% for this -- making a range of 300 to 3,000 for a city of 3,000,000 on average (the rough size of Toronto, Ontario). I would also expect some clustering of populations, with groups gravitating to the environment best suited to them unless everybody is absolutely territorial about their lands. The distribution will not be even, but at the same time, everyone won't be in one neighbourhood.

I don't have any facts, research, or articles to support this, because the correct answer is potentially that two people can keep a secret of one is dead.

Note this is just the supernatural population. There is probably that many mundanes that are aware of things, either through marriage or research, or shady deals with people that live way too long to be healthy. Also this will probably require modern governmental intervention if there are groups that live an exceptionally long time -- a 500 year old vampire is not likely to have a valid birth certificate or social insurance number from a country that exists today. If they did, who would believe it when they go buy something big?

That should also be enough people in the know to have enough that want to threaten the Masquerade but not necessarily enough to make a organized coalition that will inevitably take it down without a massive amount of help.

Answer 4

can also pass for human to most people

I don't get the problem. As long as they can pass for human for 9 hours a day in daylight then they can move among the population and have a normal job. "When in Rome" as they say.

"The Masquerade" is for vampires. The reason vampires need it is that:

1. They prey on humans
2. They can't pass for human in daylight
3. They need to be in contact to maintain their social status and make sure new vampires know who is in charge

Your supernaturals' ability to pass entirely for human (?at will) means there's no need for a masquerade, they just get a job and get on with life.

because they can reproduce with humans or can reproduce non-sexually (i.e., vampire or werewolf bites) inbreeding or difficulty in finding mates to continue the species is not a concern

This means they don't even need to identify themselves to each other. Each can be an anonymous person alone.

In summary:

Your fundamental setup has negated the reason to have a masquerade at all. Each can act alone in human society and is responsible for their own anonymity. There's no basic requirement for coordinated action. You have created no practical limit to their population, it could even be everyone, humans having died out centuries earlier, and nobody would know. Nothing to see, so nothing to hide.

What they need is a weakness

They need a reason to have a society of their own. They need some set of circumstances where they are involuntarily exposed and need a group responsible for cleaning up the mess before it's uncovered. Some varieties will need to be able to reveal themselves to others to reproduce. Perhaps there should be competition for some resource between varieties so they have reason to act against each other in groups while all covering up the existance of all of them.

Answer 5

Answer: Close to 3% of population is the max, in order to hide anomalities caused by unique patterns of consumption of economic goods caused by their non-human nature.

Imagine society where all population is isolated from one another(probably with exception for the closest family members, like children and their parents. They would be living under the same roof until their child becomes mature enough), all interactions are online, over the Internet. From the youngest age you're indocrinated to believe only information from trusted government-apporved sources (sites, electroinic books, electronic films, etc), which are heavily moderated to delude normies into thinking that supernaturals don't exist and that their existence is impossible. The rest of the mediaspcace (i.e. sites, books, films, etc, not approved by the government) is filled with alleged trolls, insane people, liers, foreign propaganda bots, etc (probably the government will pay people to fill it with nonsense and trolling in order to make aura of untrustworthiness stronger). The reputation of this part of the media is extremely low. And to make it even lower there are secretely paid by government, heavily moderated, forums where "skeptics" "debunk" information from unapproved parts of media space. If an average normie will see, let's say, a blogpost that tries to prove that supernaturals exist, then at the best they will think that it's some kind of an intricate lie that can be debunked by "skeptics" anyway, so why bother reading it? If it will have videos or photos, then the normies will think that these videos and photos are fakes. If it will be just a text with a witness testimony of existence of supernaturals, then normies will think that the person is a troll or a mentally ill person. Also there will be government-paid "crackpots" that will preach that supernaturals are real with bogus logic, weak evidence (so "skeptics" would be able to "refute" them), and also belive in obviously insane things, like that the Earth is flat, in order to create assosiation of existence of supernaturals with with crazy ideas ("So, you believe that supernaturals are real? Then maybe you also believe that the Earth is flat?")

Answer 6

The part about the goverment aiding or at least not interfearing could be solved by some kind of anchient aggrement. The supernatural don‘t interfere with „the system“ and „the system“ leaves them alone. This aggrement came about in the long ago, after both side clashed horrible and came to some kind of mutally assured destruction. This aggrement is only in peril in times of unorderly change, like the russian revolution. Then the new rulers need to be „convinced“. When there is an orderly change of power, like the german revolution of 1918, then old and new rulers will take care of this because it is in their own best interesst.

Hidden population

What means hidden exactly? More then the more private parts of the sexual deviant, a community that exists but usually only the in-group knows about. But the general public is aware, that these groups exist. To change that, you‘ll need some kind of trick. My suggestion, the existance of the supernatural is a conspiracy story. There are people believing in this, and have been for centuries but if the society treads them as lunatics, the supernatural are safe. The biggest problem with this is, that we have good vision capturing systems (cameras) for something like 30 years. So you need a way to make videos and photos disbelievable, maschine learning could provide the usual „fake“ excuse. Just make computers in your world faster sooner, so that what is now hot science becomes established tech available to everyone with a gaming computer. Voila photos and videos mean nothing.