Facebook has shrunk the “degrees of separation” between people from six to four, a study has claimed.

Since social psychologist Stanley Milgram conducted an experiment in the 1960s, it has been widely accepted there are six degrees of separation between many people.

But Facebook’s data team, in collaboration with researchers from a Milan university, has found there are now, on average, four degrees of separation between people on Facebook.

The study assessed the relationships between 721 million active Facebook users and their 69 billion friendship links.

“First, we measured how many friends people have, and found that this distribution differs significantly from previous studies of large-scale social networks”, the Facebook data team said. “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.”

The researchers said the most distant Facebook user in the Siberian tundra or the Peruvian rainforest was probably no more than a friend of a friend of a friend of a friend of a friend.

They used algorithms to approximate the number of links between all pairs of individuals on the site and found 92 per cent can be linked by four degrees, meaning two people are connected by no more than four friends. Six degrees of separation refers to the idea that everyone is on average six steps away from each other.