In 2008, there were 5.28 degrees of separation between any two Facebook users. Today, there are 4.74, the studies found. (CBC)

All 721 million active Facebook users worldwide are connected to each other through an average of just 4.74 friends, friends-of-friends, and other intermediaries — significantly fewer than six degrees of separation.

And the number of people separating them is shrinking, say the findings of two studies released online late Monday by Facebook, researchers at the Università degli Studi di Milano in Italy and other collaborators.

Today's average of 4.74 degrees of separation or "hops" is already smaller than the average distance of 5.28 hops in 2008, Facebook reported in a blog posting.

6 degrees of separation

Hungarian author Frinyes Karinthy first proposed in a short story in 1929 that any person could be connected to any other person in the world via just six intermediate connections – friends, friends-of-friends, friends-of-friends-of-friends, etc. U.S. psychologist Stanley Milgram tested the idea in the 1960s with a series of experiments where volunteers were asked to send a message to a person they did not know by passing the message on to someone who was more likely than themselves to know the final recipient. The next person who received the message would repeat the procedure. In many cases, the chain was broken by people who refused to play along, but in the cases that worked, the average number of steps was 5.5.

The average distance between U.S. users was just 4.3, said the first study, whose lead author is Johan Ugander, a PhD student in math at Cornell University and a former research intern with the Facebook Data Science team.

Worldwide, "fully 92 per cent of all pairs of Facebook users were within five degrees of separation," the study said.

Some other findings of the studies:

  • There were 69 billion friendships among the 721 million active Facebook users, who represent a little over 10 per cent of the global population.
  • The median friend count is 100 and the mean is 190.
  • 84 per cent of connections are between users in the same country.
  • Friends tend to be about the same age — even for users aged 60, the distribution of their friends' ages "sharply peaked at exactly 60."

Facebook billed the studies as the "largest social network studies ever released."

It also noted that unlike previous studies of social networks involving subjects who could not see the whole network, the researchers had the data to be able to choose the shortest path between any two individuals.

The new studies were posted on the online scientific article archive Arxiv. There was no indication about whether they would be submitted to a scientific journal for publication and go through a peer review process.