Sharing concrete compensation numbers with co-workers and even peers at other companies is a good way to stoke resentment and bitterness--both in yourself and with others. Especially if you're not prepared to move on if you find you're making less than those around you. I learned long ago to actively avoid learning others' compensation.

It's a real dilemma. On an individual level fair pay is whatever you're willing to accept; what those around you are paid is completely irrelevant. On an aggregate level lack of transparency helps to persist systemic discrimination.