Facebook shrinks the world down to four degrees of separation

22 Nov 2011

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Once it was believed that most of us were six degrees of separation apart. But now data boffins at Facebook have surmised that because of social networking that idea is defunct and we are now likely to be only four degrees of separation.

In what is believed to be the largest social network study ever conducted, Facebook studied all 721m active Facebook users – more than 10pc of the global population – who between them have 69bn friendships.

According to Facebook, only 10pc of Facebook users have less than 10 friends, 20pc have less than 25 friends and more than 50pc have more than 100 friends. The average friend count is 190.

The idea of six degrees of separation was put to the test in a short story by Hungarian writer Frigyes Karinthy and Stanley Milgram in the 1960s, who selected 296 volunteers and asked them to send a message to a stockholder living in Boston indirectly by way of a personal acquaintance to was more likely to know the sender.

Milgram found that the average number of intermediate people in these chains was 5.2 – or six hops – proving that there are few degrees of separation between any two people.

The Facebook study, using state-of-the-art algorithms developed at the Laboratory for Web Algorithmics of the Università degli Studi di Milano, was able to prove that six degrees actually overstates the number of links between typical users.

A friend of your friend knows my friend

While 99.6pc of all pairs of users are connected by paths with five degrees (six hops), 92pc are connected by only four degrees (five 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.

“Thus, when considering even the most distant Facebook user in the Siberian tundra or the Peruvian rain forest, a friend of your friend probably knows a friend of their friend,” Facebook’s data team said.

“When we limit our analysis to a single country, be it the US, Sweden, Italy, or any other, we find that the world gets even smaller, and most pairs of people are only separated by three degrees (four hops).

“It is important to note that while Milgram was motivated by the same question (how many individuals separate any two people), these numbers are not directly comparable; his subjects only had limited knowledge of the social network, while we have a nearly complete representation of the entire thing. Our measurements essentially describe the shortest possible routes that his subjects could have found,” Facebook’s data team said.

One can’t help but wonder what Facebook’s data team would make of a small population like Ireland, where most of us are globally connected by virtue of culture and history but usually just two or three degrees of separation apart.

This theory might already have been borne out during the summer when it was already news here that Facebook CEO Mark Zuckerberg was in Ireland before he finished his first pint of Smithwicks in a Dublin pub.

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Editor John Kennedy is an award-winning technology journalist.

editorial@siliconrepublic.com