Facebook makes world smaller 6 degrees, A theory stemming from an experiment by social psychologist Stanley Milgram in the 1960s claims every living person is connected to any other through only six friends. According to a recent study, Facebook reduces the six degrees of separation to only four, meaning the world's largest social network makes the world even smaller (figuratively).
The study, a joint effort by Facebook and Università degli Studi di Milano, shows that the number of "hops" separating any two persons on Facebook is in fact smaller than six. According to the study, "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)," with the average "distance" between users getting smaller over time.


In popular culture, the best known implementation of the "six degrees of separation" theory is the Kevin Bacon game, which requires you to connect a Hollywood actor to Kevin Bacon, with actors being connected if they've been in a movie together. The higher the number of "hops" between an actor and Kevin Bacon, the higher that actor's "Kevin Bacon Number" is.

The game can be tested at the Oracle of Bacon, a web application that uses information from the Internet Movie Database to calculate the number of links between an actor and Kevin Bacon. The site says that Kevin Bacon Numbers over 4 are very rare, with the average number being 2.981. It could be a coincidence, but Facebook's latest findings show that the Kevin Bacon game provides quite an accurate representation of relationships in a social network.

Facebook has also published the results of another study, which looks at the average number of friends on Facebook. According to the study, "10% of people have less than 10 friends, 20% have less than 25 friends, while 50% (the median) have over 100 friends."

However, the distribution is skewed, so the average number of friends is 190. It might seem low to a lot of users, but it can be explained with a phenomenon explored by sociologist Scott Feld in 1991, which shows that people usually perceive their friends to have more friends than they do.

Facebook's study shows that even on an online social network that is supposed to cross the boundaries of geography and age, people tend to befriend others their own age, as well as people in the same country.

Finally, Facebook's research shows that if you limit the analysis to a single country, the "four degrees of separation" theory shrinks even further, with most pairs of people being only separated by 3 degrees.