This one is tricky. H1B visa holder salaries are transparent. And, they tend to make less than their US citizen peers. But, I guess it would need to be transparent for everyone for it to work out. There have been companies that have done it, but they've often already been focused on treating everyone fairly before or as part of the move to transparency. If the goal of the company is not to engender a team spirit by treating everybody as well as possible, but instead to maximize profits, then it would likely tend toward executives trying to keep pay low across all employees and would limit their willingness to hire outliers who demand very high salaries.

I don't know, is what I think I'm trying to say. There hasn't been a lot of data...very few companies are open about the salaries they pay, and there is a definitely hesitation among employees about discussing their salary (and it is often discouraged by the company, to boot).