The concept of a tightly knit, interconnected world — one where an individual’s connection with another is within six degrees of separation — has been around for nearly half a century. Social psychologist Stanley Milgram published his findings in 1967, and has been a standby of sociology and pop culture alike ever since.

It comes as little surprise, then, that the rise of social networks over the past decade has brought us even closer together. Facebook released two studies of its social graph on Tuesday, which conclude that we Facebookers are closer to one another than we thought.

In collaboration with academic researchers at the Università degli Studi di Milano, Facebook’s study found that instead of the average of six degrees of separation between each of us, Facebook users are separated by an average of four degrees.

There’s something of a difference between the two test groups. Milgram’s initial sampling put 296 persons to the test of sending a postcard to a given individual, but only by using one’s existing network of connections — and those connected to her connections, and so on — to reach said individual. Facebook studied its entire social network composed of nearly three quarters of a billion members, ostensibly giving a more accurate idea of just how short the distance is between two given people.

“Every new user that joins Facebook is a potential short-circuit that makes the path between others shorter,” said Lars Backstrom, a software engineer on the Facebook Data Team who co-authored the paper, in an interview.

During the study, Backstrom noted, the researchers discovered another interesting corollary. While the number of degrees of separation between users across states, countries and even continents lessened, the majority of our friends are clustered around us locally, with 84 percent of all connections are between users that live within the same country.

“Yes, there’s all of these shorts paths between us,” Backstrom said. “But there’s also this sort of strong community structure as well.”

Backstrom concedes that however fewer degrees of separation there may be, it remains difficult to gauge the “quality” of the connections between users. “All of your friends aren’t created equal,” Backstrom said. A June study conducted by Pew Research found, however, that of the four major social networks surveyed (Facebook, Twitter, LinkedIn and MySpace), Facebook users tend to have closer relationships with one another. Take note, though: Google+ wasn’t around quite yet when the survey took place.

Ultimately, says Backstrom, the research aims to further the understanding of social networks. “We look forward to continuing to illuminate social trends and helping people understand how the world is becoming more connected,” the Facebook Data Team wrote in its blog post.

Photo courtesy of Facebook