If it feels like a small world, that's because it is.
A new study of Facebook data by researchers at the University of Milan has shrunk the "six degrees of separation" theory, which posited that any two people are separated by just six acquaintances.
The analysis of 721 million active Facebook users and their over 69 billion friendships found that any two individuals in the world are connected, on average, by just 4.74 acquaintances.
"[W]hen 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," Facebook's data team wrote in a blog.
The "six degrees" theory was first proposed in the 1920s and put to the test in 1967 by social psychologist Stanley Milgram, who asked 296 people scattered throughout the United States to each send a letter to a specific individual in Boston by routing it through acquaintances they thought were likely to know the person (the concept also gave birth to the game "Six Degrees of Kevin Bacon," which challenged players to connect Hollywood stars to Kevin Bacon). The University of Milan's Facebook study took a month and, according to the New York Times, the researchers "used a set of algorithms developed at the University of Milan to calculate the average distance between any two people by computing a vast number of sample paths among Facebook users."
Ninety-two percent of individuals on Facebook are just "four degrees" from one another, while 99.6 percent are separated by 5 degrees, Facebook noted in a blog post. That number shrinks even more if the pairs are limited to a specific country: while Milgram's research found that two people in the U.S. were separated by approximately six degrees, the University of Milan study concluded that Facebook users from the same country are separated by only three degrees.
Facebook's data team offered a caveat for the the findings, noting, "It is important to note that while Milgram was motivated by the same question (how many individuals separate any two people), these numbers are not directly comparable; his subjects only had limited knowledge of the social network, while we have a nearly complete representation of the entire thing. Our measurements essentially describe the shortest possible routes that his subjects could have found."
The researchers presented several additional statistics that shed light on users' behavior on Facebook.
People on Facebook tend to cluster themselves by nationality and age, though not by gender, the study found. According to Facebook's blog post, 84 percent of connections are formed between users in the same country.
Just half of all Facebook users have over 100 friends, while 20 percent of users have fewer than 25 friends. People on Facebook have 190 friends, on average, though that number is skewed upward. According to Facebook's own tally, the average user has 130 friends.