What Do We Get Wrong About Markets?

The most interesting thing I think that markets related is probably what's going on in economics. Fundamentally, we assume certain things about how money and markets work. A big one is that when you average something over time, you end up with similar answers to when you average things over populations. The connection between those is the ergodic assumption. As I understand it, and if I'm wrong, I'm sure people will send me hate mail.