From http://allendowney.blogspot.com/2015/08/the-inspection-paradox-is-everywhere.html:
Airlines complain that they are losing money because too many flights are nearly empty. At the same time passengers complain that flying is miserable because planes are too full. They could both be right. When a flight is nearly empty, only a few passengers enjoy the extra space. But when a flight is full, many passengers feel the crunch.Once you notice the inspection paradox, you see it everywhere. Does it seem like you can never get a taxi when you need one? Part of the problem is that when there is a surplus of taxis, only a few customers enjoy it. When there is a shortage, many people feel the pain.
This article gives multiple examples (including computations) of the Inspection Paradox (also known as the Friendship Paradox), meaning that even the simple concept of “average” can be a little elusive. See also http://www.technologyreview.com/view/523566/how-the-friendship-paradox-makes-your-friends-better-than-you-are/
Mean Green Math 