The real solution to the problem is everyone needs to share their income level with their co-workers as well as their performance reports. And don't be afraid to leave!
I think happiness levels in companies would definitely skyrocket...
Wonder what the experience in Sweden is, though. How often do people query their Coworkers salaries there?
Certainly, for example with men and women, there would be physical tasks were women can not reach the level of men.
Depending on the culture of the company/country people is more or less willing to share salary information. But there is always people that does that, and it becomes awkward when the manager counted with all salaries being secret.
Don't assume salary secrecy, people talks.
This doesn't seem like such a bad outcome.