[egsec]

It may be zero sum or not zero sum depending on different situations.

If all employees values transparency and fairness and would rather have a lower but more fair pay, them the transparency may work.

However, the employer typically derives more profit per unit of work if they employee makes less. Also, if you are a good negotiator or you are the type to always threaten to leave if not given more pay you benefit from the opaqueness. If the company has a lot of good negotiators it may make sense to be more transparent to keep the overall wages down since no one can exercise that benefit.

There are probably other factors such as supply and demand beyond individuals at specific points in time which need to be taken into account (surge pricing?) we need someone for this project now, so we will pay them a premium even if we would normally pay them the same as everyone else, even in consideration of long terms costs this may make sense.

[nickff]

You implicitly assume that the employees would all (or net) make more money under a more transparent system, and I am not sure why. It may be true, but some may also accept smaller raises if they know most coworkers are at a lower salary. I can imagine a number of effects that transparency may have, and do not know their net impact.