How big can a town get before everyone stops knowing everyone else?

Question

In small towns, people often say that everyone knows everyone. While probably not literally true (for all but the smallest towns), the rate of interaction between members of the town is still high enough to create this perception.

The two main variables I can think of are the population density of the town and the rate of activity in that town. A small island with people living close together and working close together (say, near shore subsistence fishing) is more likely to produce this sensation than say a small frontier town whose principle industry is cattle.

For the sake of keeping things simple, let's say that our small town has a population density of 100 people per square mile (a bit more than half as dense as anchorage) and the rate of activity is moderate. People see each other when they go out to dinner, to the market, or for communal events like sports but not necessarily every day.

How many people can our town get before the sense of "everyone knows everyone" is lost?

Answer 1

The number you are looking for is Dunbar's Number.

It is well-known for most primates, but only approximately for humans (between 150 and 250).

Humans of course have prodigious memory, and might be able to memorize the names and faces of far more than that (probably into the low thousands). But to actually know someone in a meaningful way, this is the Dunbar number.

Answer 2

The number you are looking for is not Dunbar's Number

Dunbar's number is about how many relationships you can maintain, but does not directly dictate the "sense" of knowing everyone. Another relevant figure is that the average person can recognize 5000 people's faces; so, as long as you recognize everyone you encounter, and know enough of them to feel compelled to engage with someone everywhere you go, then the "sense" of knowing everyone is preserved.

This means that the actual size you are looking for is going to be somewhere between 150-5000 (if not higher), but where it that range it falls will depend a lot on various practical and cultural factors.

First of all, how many people you can know is not so much how many people there are, but how many people you must interact with. Even in a small town, most people only know their immediate neighbors plus people who they share a joint activity with. The key here is the joint activity. Generally speaking, the 4 joint activities that bind small towns are a single school, a single church, a single industry, and/or a single popular recreation. If you have all 4, then you will generally be able to connect with enough people from at least 1 of these places to always feel like you know someone everywhere you go.

Schools:

For a school to really create this effect, it is best to have a 1 class per grade structure which maxes at about 30 students per grade level. Since ~18% of the World's population are school aged children, and they can be divided into 12 Grade Levels. This means that each grade represents about 1.5% of your total population; so, a single class/grade school system can support a total population of about 2000 people. This would guarantee that you would know everyone in your own generation, and probably most of the children and parents of children in your children's generations. While this is not enough to actually know everyone in town, people tend to congregate in places that are popular within their own generation; so, if everyone in the same high school class used to go to the same diner as kids, then as adults, they will likely continue to go there and continue to run into the same people over and over again strengthening the sense that they know everyone.

Churches:

Churches are generally better than schools at uniting people between different generations and backgrounds than jobs or schools, but they tend to make who you connect with much more optional. As such, you tend to see that churches with congregations bigger than Dunbar's Number do often form many smaller communities of acquaintances rather than a single unified church community. So, a church will generally not help you know everyone well in a larger town better, it can help connect you with generations of people you would otherwise not know. If a church is the only unifying factor your town has, then your limit may in fact be closer to Dunbar's Number, but when paired with other unifying factors, their ability to form cross generational relationships may make you feel more like you know everyone, because you will internalize that you know people outside of your inner circle.

Industries:

Like churches, these can do a good job of bringing together on the scale of Dunbar's Number before some of the people you share a work area with are just strangers to you. However, unlike a church, there is not as big of a spread of demographics since you will only be working with people of working age. This can leave bigger gaps in who you do not know, but also serve more as a linchpin to become familiar with more people indirectly.

Common Recreation:

The fewer popular recreations there are in an area, the more likely you are to have a shared interest with someone who is otherwise a stranger. Let's take American football for example. In many small American towns you do not need to really know someone to start talking to them about the the local football team. One of the biggest elements of feeling like you know everyone is having a common language for breaking the ice when you do encounter someone new (or who you only know by face), and common recreation is great for that. So, sit down next to a stranger and they lean over and ask if you saw the game last weekend, you answer "yes", and you start to talk about it. You don't really know that person but you maintain the feeling that you kinda do because you have a shared experience to discuss.

This leads into the final key to this question which is how people process the sense of knowing everyone. Human nature works on the pieces of information we choose to process and not the information we choose to ignore; so, you only need to know 1 person wherever you go, and not spot too many people you do not recognize at all to feel like you "know everyone".

So, if every time I go somewhere and there are 20 familiar faces, a couple of total strangers, and just 1-2 people I actually know on a personal level, this is good enough to maintain the sense of knowing everyone.

The real wild card here is population density though. 100/sqmi is a very low density. There will not be enough people in small enough of an area for you to want to be regularly going places you might meet people; so, out of a town of 2000, most people will stick to smaller sub communities and seem like random strangers on the rare occasion you do see them out in the world, but if you were to cram 2000 people into small town center, it is much more likely that you will recognize most of those 2000 people.

Answer 3

In a region where people don't move, a couple thousand

If we define "everyone knows everyone" as "you recognize everyone you meet and know a fact about them" then a town of a couple thousand people is gonna be your limit. I'm talking about a medieval/ancient town, where 95% of people farm or do The One Thing Your Town Does. In the modern world it's a bit harder because of how much people can move around. At that size, "you're the blacksmith's son" or "you're Gertrude's mother" is something you could say to everybody. Dunbar's number states that a person can know 150-250 people "well." Part of "knowing someone well" is knowing things about them, like who their relatives are. In a setting where there are relatively few immigrants (meaning people from outside your town/village/county, not necessarily from-a-different-country foreigners) and few people move away, it's not at all impractical for the 200ish people you know well's immediate family to comprise the rest of your small village!

As an anecdotal example, I went to a military college. You couldn't leave often, everyone lived in the same 3 barracks, and the campus itself was fairly small. Total student body was about 1400, divided into 9 separate companies made up of members of every year. After my first year I knew every person there by sight and company, and the vast majority (excluding only the freshmen first semester, who it was beneath a "real" cadet's dignity to pay much attention to) by name. So throughout my cadetship I knew more than 2,000 other cadets. It's not a perfect example because obviously they weren't my total sphere, as I still knew my hometown friends, family in other areas, and so on. But likewise the turnover (2-300 graduates a year, 400+ new people every year) is much higher normal population turnover. But I think it's worthwhile to note that once you're stuck with the same faces and see them every day, it's not that hard to "know everyone."

As another anecdotal example, I grew up in a county of about 5,000 people. While I didn't know everyone by name, I had to have at least 3 conversations every time I went to the grocery store, had not polity nod/say hello to half a dozen additional acquaintances, and could always tell when someone "wasn't from 'round here." There the population was more spread out, not everybody did similar jobs/went to the same places, and was much larger than my college. But because I lived there longer and the low turnover rate of people moving into the area i could still tell who wasn't from my county, even if I couldn't name every person I saw who was.

Answer 4

"Everyone knows everyone" can be used colloquially in a less strict definition.

The concept that "everyone knows everyone" extends to towns larger than hundreds or even thousands. You don't need to know the entire population personally to have this feeling, you just need to be able to find multiple mutual acquaintance between any two people, and connect them.

"Oh your bosses niece goes to school with my daughter".
"Oh wow. And your girlfriend went to the same raves as my coworker".
"And we share the same therapist!"

My town (Adelaide Australia) has a population just over a million, and the feeling that "everyone knows everyone" is very much part of the culture despite "knowing a million people" being ludicrous. It's a normal experience to tell a story about one acquaintance to another and have them recognise the person.

When something newsworthy happens (eg fatal car crash) - you will know multiple people who knew the victim personally.

Maths backs this up. At any one time I was at high school with 1000 people, over 12 years I crossed paths with about 2000 people from school and high school. Another 500 from years of church and youth groups, and another 300 from hobbies and recreational activities, and another 200 from different workplaces. Lets assume I got acquainted with 50% of them. That's ~1500 people I know. If you know 1500 people too, in a city of 2.25million you can expect to have a mutual acquaintance.

Shrink the population a bit, and for populations of high hundred thousands approaching a million, you'll have multiple connections to almost every person in the city.

Answer 5

In terms of "what size of a community can be maintained without external authority", this appears to be a "few hundred". In Evans, Susan Toby. Ancient Mexico And Central America. pp. 26-27:

Furthermore, the maximum number of people with whom we can develop workable relations of trust, regulated face-to-face interaction and the presence of a mutually respected leader, during any time, is several hundred people.

In particular since knowing everybody else enough to trust them is used as a criterion for being able to maintain the community, this would also correspond to the size of your hypothetical village.

The reference therein contains also interesting discussion on community size. In particular how conflicts get regulated depending on the size of the community.

Answer 6

Question is how many people to have a sense of knowing everyone which is not the same as the topic question of recognizing everyone- the answer could be 1 million or more. If I can see 100 people per day over and over then I think I know everyone- your brain can not conceive of the people you are missing. Slums and building projects (in the old days) have the sense of knowing everyone. The factors determining it are population/commercial density, sociability/visibility and mobility. If everyone walks then you need a higher density of people, if people drive but not too fast then lower density is ok. People need to be able be seen- they work in small operations or on the street.