Some information on the use of social networking sites is extremely difficult or impossible to collect as part of a phone survey. For example, information on the structure of people’s online friendship networks, such as the number of friends of friends, or how densely connected are a person’s friends (i.e., if a person’s friends have all friended each other). Such measures, while difficult to collect in a survey, are important in understanding how use of Facebook is related to different social outcomes. For example, measures such as social cohesion (density) in people’s personal network of relations is a strong predictor of things like trust and social support – the ability of people to get support when they are in need or seeking help making decisions [8].

In this section we look at measures of Facebook use that we could only obtain from logs of people’s actual use of Facebook. Specifically, we examine how these measures relate to people’s everyday experiences outside of Facebook in terms of the amount of social support they receive, trust, and political participation.

A friend of a friend is … probably not your friend on Facebook

As the common saying goes, a friend of a friend is a friend.  But on Facebook this is the exception rather than the rule. When we explored the density of people’s friendship networks, we found that people’s friends lists are only modestly interconnected. A fully connected list of friends would have a density of 1 (everyone knows everyone else). The average Facebook user’s friends list has a density of only .12 (SD=.07). There was a maximum density of .42 (see Appendix A: Graph 1).

As an example of what this means, if you have 10 friends, the number of possible friendship ties among everyone in your network is 45 (possible ties=n*(n-1)/2). If you were an average Facebook user from our sample, with 245 friends, there are 29,890 possible friendship ties among those in your network. Our density measure of .12 means that for the average user with 245 friends, 12% of the maximum 29,890 friendship linkages exist between friends.

A network density of .12 is low in comparison to studies of people’s overall personal networks. A 1992 study found a density of .36 between people’s offline social ties [9]. We suspect that Facebook networks are of lower density because of their ability to allow ties that might otherwise have gone dormant to remain persistent over time.    

There are a number of factors that predict how densely connected a friends list is likely to be.

The longer people have been using Facebook[7. numoffset="7" Pearson Correlation -0.205; sig 2-tailed