[morgante]

In practice, I think the problem is that everyone is fundamentally a market of 1. I have never seen a salary site (including Glassdoor, LinkedIn, or step) come even remotely close to what I actually make.

Years of experience, education, and title are never enough to gauge performance or pay.

[mswen]

Clearly location and fairly granular skill profiles would help. Other factors that might help include the type and size of the company.

Can you think of other factors that would help?