Degrees of separation? Under five, and falling

Posted by Emma Woollacott

When it comes to Facebook, it seems we're not all linked by six degrees of separation - the true figure is actually 4.74.

Facebook and the University of Milan have analyzed the networks of all 721 million active Facebook users, and found that 99.6 percent are connected by five degrees - or six hops - and 92 percent by four.

"Thus, when considering even the most distant Facebook user in the Siberian tundra or the Peruvian rainforest, a friend of your friend probably knows a friend of their friend," says the team.

"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 3 degrees (4 hops)."

Stanley Milgram's original 1967 experiment asked 296 volunteers to attempt to reach a target person by sending a postcard to the person they thought likeliest to know the target, then asking that person to do the same.

Facebook points out that its own experiment is somewhat more efficient, as the original volunteers might not have picked the fastest route, whereas the Facebook algorithm is able to pick the best route every time.

Either way, the world seems to be getting smaller. When the researchers ran the data for 2008, they found that the average distance was 5.28 hops, compared with today's 4.74.

The research also threw light on the perception many of us have that our friends are more popular than us.

"A classic paradox regarding social networks dictates that, for most people, the median friend count of their friends is higher than their own friend count," says the team.

Ten years ago, Scott Feld wrote a paper entitled 'Why Your Friends Have More Friends than You Do', showing that college students typically find that their classes to be larger than the average class size, and that when sitting on an airplane, it will typically be more crowded than average.

"These effects all arise because for people, classes, and flights to be popular, you must be much more likely to choose them," says Facebook.

"So you shouldn’t feel bad if it seems like all your friends are more popular than you: it appears this way to most of us."

The two papers are available here and here.