Why do you assume someone making less is being "screwed over"? Imagine employees A and B. B greatly outperforms A and therefore rightly makes more. However, A is delusional about his skills and thinks he is as good as B. Pay information is made transparent and A sees he is making less. This makes him mad because by all rights he ought to be making as much as B! This type of comparison/resentment might make A want to quit or ask for a raise, whereas before he was both content and fairly paid at his performance level.