You wouldn’t have to negotiate a better salary if it would be obvious that you are underpaid.
I have people who work on my teams who are absolutely fantastic and, while already well-paid, probably should make more. I have other people on my team, with the same title, same education, same on-paper responsibilities, same city, same years of experience, who might be below the median pay and are still overpaid based on my estimation of their contributions relative to their peers.
You can't look only at a spreadsheet and determine that it's "obvious that you are underpaid", IMO.
This is 100% a red herring as far as pay transparency is concerned anyway. If you're not being unfair you have no reason to hide anything.
It actually extends to the whole market, too - if all salaries are transparent, then an RN makes x. They can't make more than that, anywhere they go. It gives a floor, sure - if they get hired, they'll get paid the same as everyone else; it just also makes a ceiling, and, I believe, may slow income growth in general.
So I'd see your point as already happening, companies have already capped salaries, except for executives, who basically set their own salaries.
I love seeing this statement. It's true but the people who post it never follow up evaluating whether or not productivity growth has far out-paced the rise in living standards. If productivity growth has been exponential while the rise in living standards has been linear that's a sign that there's a problem regardless of whether or not living standards have risen.
That means that transparency works _for_ you, not against you.
Think of it like this. Will you be willing to post your entire web browsing history to a publicly available archive regularly? It will help prevent a lot of illegal activity if everyone agreed to do that.