"Say what? The companies already know how much they're paying everyone else. The only one who doesn't know is you."
I'm talking about company A knowing all of the salaries of company B and C.
Here is a link I found talking about Swedish salaries (2012):
http://lostinstockholm.com/2012/01/10/average-salaries-in-sw...
Most salaries for all occupations across the board are almost the same. I believe this is one of the results of public tax/salary information.
"Because you can make a convincing argument that you're worth 20% more."
Like I said, if everything is public, it won't matter. If I see that all of my competitors are paying 20% less (which won't be difficult to aggregate with everything public..a search engine for employers will popup in no time) I know that even if the potential employee goes somewhere else, they won't get a higher wage. Why would I pay them any more?
On an Individual basis, I can also figure out exactly what you were paid at your last job (instead of guess work/relying on what you are asking). If you were paid $50K at your last job, why am I going to pay you $70K?
"The powerful already have those tools. This is about giving those same tools to the less powerful as well."
As an individual, privacy is a great tool to have at your disposal and is one of the only ways to defend against powerful companies taking advantage of you.