Are you a social butterfly or a tortured introvert? Maybe it doesn't matter. Check this out:
List all of your friends.Â Then ask each of your friends how many friends they have.Â No matter who you are, whether you are a man or a woman, where you live, how many (or few) friends you have, and who your friends are, you will very likely discover that your friends on average have more friends than you do.
It's humbling, isn't it? The reason is simple, once you think of it. You are most likely to make friends with a friendly person! You can check the link above for other instances of this social asymmetry.
It turns out that this isn't just interesting -- it's useful. You can use this property of friendship to get advanced notice of outbreaks of communicable diseases like the flu. This article reports a study among Harvard undergrads that shows how checking the doctor visits of the friends of a random sample of students gave a two-week warning of a flu outbreak.
I love it when such a simple idea turns out to have such practical implications.
(My thanks to The Big Think for bringing this to my attention.)