Nov 28 2011

Four Degrees of Seperation

When you live in a country town, you soon learn that everyone is directly connected to everyone else.

Even in a large city like Sydney, its unusual if someone you meet doesn’t know a friend of a friend.

But did you know that if you meet a stranger anywhere in the world, whatever remote spot, its likely that a friend of a friend of yours will be a friend of a friend of their’s?

The film ‘Six Degrees of Seperation’ postulates that everyone in the world can be connected to anyone else through six hops. A 1960’s study by Stanley Milgram involving 290 people seemed to confirm this.

The Facebook data team have anaylsed the connections between all 721 million active Facebook users (more than 10% of the global population), with 69 billion friendships among them.

Using state-of-the-art algorithms developed at the Laboratory for Web Algorithmics of the Università degli Studi di Milano, we were able to approximate the number of hops between all pairs of individuals on Facebook. We found that six degrees actually overstates the number of links between typical pairs of users: While 99.6% of all pairs of users are connected by paths with 5 degrees (6 hops), 92% are connected by only four degrees (5 hops). And as Facebook has grown over the years, representing an ever larger fraction of the global population, it has become steadily more connected. The average distance in 2008 was 5.28 hops, while now it is 4.74.

Which confirms two things.

It is a small world, after all.

And If you can’t say something nice about someone, don’t say anything at all/ It’s sure to get back to them in just a few hops.…


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