One of my favorite sociology articles is Scott Feld's article "Why Your Friends Have More Friends Than You Do ," published in the American Journal of Sociology in 1991. As the title of his paper promises, using logical deduction and ample data Feld shows that your friends are indeed more likely to have friends than you do (i.e., that the average number of friends of friends is always greater than the average number of friends of individuals). Why is this, though? To put it as simply as possible, the reason is that you are more likely to be friends with popular people than unpopular people. To confirm this for myself, I quasi-randomly selected ten of my friends on Facebook. Here is the sum of the friends of my friends in my sample:
358 + 271 + 694 + 104 + 403 + 315 + 302 + 891 + 83 + 1,986 = 5,389.
Dividing this total by ten (the size of my sample) equals 538.9, well above my 400 or so friends on Facebook. Even with this small quasi-random sample, the phenomenon holds!
An unexplored (as far as I can tell) corollary of Feld's finding is that any characteristic correlated with the number of friends a person has would also appear greater among your friends. For instance, if having more friends means being more extroverted, then on average your friends are going to be more extroverted than you. Similarly, if having more friends means being taller or better looking, than your friends will also be taller or better looking than you.
A related issue is the so-called class size paradox: you are more likely to be in a classroom that has more students than the average classroom. Likewise, you are more likely to be on a beach more crowded than average, or in a movie theatre more crowded than average.