Friendship Paradox

• The friendship paradox is the phenomenon first observed by the sociologist Scott L. Feld in 1991 that, for almost every person, that person's friends have more friends than they do.  In spite of its apparently paradoxical nature, the phenomenon is real, and can be explained as a consequence of the general mathematical properties of social network graphs. However, it may also be the cause of a number of social misconceptions.

• The paradox is explained by the fact that one is more likely to be friends with someone who has more friends and less likely to be friends with someone who has fewer friends.
• This observation has been used as a way to forecast the course of epidemics.

Source: wikipedia.com