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I’m often asked at workshops: How big should my network be? And in the past, I tended to reply somewhat sarcastically: How long is a piece of string? In other words, if you ask a silly question, you get a silly answer.

But on reflection, the question isn’t quite so silly, especially if it is rephrased like this: “How big a network can I actually maintain?” The right answer is: about 150.

If this sounds simplistic, you might be interested to hear about research by Robin Dunbar, Professor of Evolutionary Anthropology at the University of Oxford. He has discovered that our social world is actually much more limited than we might expect. Despite the fact that for the past couple of hundred years most of us have been living in ever-larger cites, average network size remains around 150. (But please be aware: the number is by no means exact, and can be over 200.)

To check his findings, Dunbar looked at all sorts of data sources. Most tribal societies today live in groups of around 150. Average village size England in the year 1087 (as recorded by William the Conqueror’s Domesday Book) was 150. In many armies the smallest standalone unit (the Company in the British Army) is around 150 people. And if you look at the parish records for English counties in the 18th century, in each one the average village size is 150 (except, inexplicably, for Kent!).

Who are these people? Actually, each network of 150 people can be broken down into smaller groups. Firstly, most of us have a small circle of about 5 people with whom we are intimate. Then we have about 15 good friends, about 50 friends, and in the region of 150 acquaintances. Interestingly and again inexplicably, each level seems to increase by about a factor of 3.

Each category includes the previous ones, rather like the concentric ripples created by a pebble thrown into a lake (where you, of course, are the pebble at the centre). The first three groups (intimates, good friends and friends) are fairly self-explanatory – but the outer circle of acquaintances are especially interesting, from a networking perspective.

Dunbar describes these acquaintances in two ways. On the one hand, they are people with whom you have some sort of relationship; they aren’t just names and faces. To use Dunbar’s own phrase, they are people with whom you could easily have a drink if you ran into them in the transit lounge of Dubai airport in the small hours.

Another way of describing them is to do with face time. These are people with whom you do things. People from whom you could ask a favour and have a reasonable expectation of a positive reply.

Why so few?
Why is our social world so restricted? Dunbar thinks there are two reasons. One is simply a time constraint. There are only so many hours in the day, after all, and so the time we can spend, face to face with friends and acquaintances, is by definition limited. However much we may want to invest in our relationships, reality gets in the way.

The second constraint is cognitive, to do with brain size. When studying primates, Dunbar found a clear correlation between brain size and group size; it follows that we are simply not capable of keeping track of more than about 150 relatively close contacts.

Facebook friends?
Dunbar, along with many other academics, argues that face to face contact is crucial to relationship building. Technology – from the telephone to email and social media – is great at helping us keep relationships going, especially in our spread-out world where we may have been born in one place, went to college somewhere else, and end up working in a third place. They help to prevent relationships decaying if you’re too far apart to go to the pub together – but, in the end, if we don’t manage to get to the pub occasionally, the relationship is likely to wither away.

So if you know anybody who claims to have 1000 Facebook friends, you know they must be kidding themselves. While people clearly vary in their ability to manage relationships, such extremes are (almost certainly) just not true. Being invited to a party, as I once was, with 2,000 of my host’s closest friends was fine – so long as I realised that ‘close’ wasn’t meant to be taken literally. Those hundreds of Facebook ‘friends’ aren’t even acquaintances; they’re more like entries in a database.

Facebook themselves have confirmed Dunbar’s general finding. It seems that the average friend count is 190, and 50% of people have about 100 Facebook friends.

Practical implications
We’ve always said that simply connecting names and business cards isn’t the same as building a professional (or personal) network. A database isn’t a network. And we also stress the importance of your weak ties, which are roughly equivalent to Dunbar’s acquaintances. Pay attention to your active network, nurture it and make sure you invest sufficiently by keeping in touch (both face to face and electronically).

Realise, too, that all Dunbar is proposing is an average. So if your network is very small, you may need to invest more time and effort. And if your network is large, be thankful that you are probably a natural connector, able to maintain a wide-ranging network relatively easily.

Take a look at your own network, and let us know if Dunbar’s number holds true for you.