Facebook Finds That People Are Only 4 Degrees Apart

Facebook scientists, yes there exists such a thing, teamed up with fellow scientists over at the Università degli Studi di Milano to find out just how close two random people on Facebook were, i.e. how many degrees of separation there are between them.

It is an accepted fact, based on some older research, that two human beings are only six degrees apart, it only takes five people to reach one another solely through their friends and friends of friends.

The idea comes from the famous "small world experiment" from the 1960s. Facebook set out to find out whether, in the highly connected and networked world of today, that still holds true.

Earlier this year, Facebook took its entire pool of active users, 721 million of them at the time, and processed all of the friendship relations between them, 69 billion connections in total.

"First, we measured how many friends people have, and found that this distribution differs significantly from previous studies of large-scale social networks," Facebook wrote.

"Second, we found that the degrees of separation between any two Facebook users is smaller than the commonly cited six degrees, and has been shrinking over the past three years as Facebook has grown," it said.

"Finally, we observed that while the entire world is only a few degrees away, a user’s friends are most likely to be of a similar age and come from the same country," it added.

Of course, since all of the people in the study are Facebook users, they are only representative for their group, i.e. the average person is likely less 'connected' than the more than 10 percent of the human population Facebook looked at.

Facebook found out that the average user has about 100 friends. That is enough for 99.6 percent of all pairs of users to be separated by only six hops, five degrees.

92 percent were connected by four degrees, five hops. In fact, the number has been shrinking as Facebook grew larger. It says that the average was 5.28 hops in 2008 while it is now 4.74 hops.

What's more and hardly surprising, when limiting the connections to people in the same country, Facebook determined that the average two users were separated by only three degrees, four hops.

The results of this study are very important if only because it is the first time anyone has done anything approaching this scale. However, as Facebook notes, the results are not strictly comparable with previous studies for two main reasons.

First, as stated above, Facebook users are not representative for the average person on Earth. Second, Facebook had access to absolutely all connections and was able to calculate the shortest possible 'distance' between two people.

In the "small world experiment" people had to choose a friend who they believed would be more likely to be closer to the person they were trying to reach, which may not have always been correct.