I just asked a coworker how much she makes (she's permanent and higher ranked while I'm temporary) and she told me it was personal. I immediately backed off – since she gets to decide what she discloses – but this left me with a nagging question (I won't press her on it). Why do people treat their salaries like a closely guarded secret even though making it open helps fight things like pay discrimination and exploitation?
EDIT: How do I fight this culture while minimizing the risk of my company retaliating?