[Infinitesimus]

No they don't. They _say_ they do (really mainly Amazon) and the rumor develops legs and gets repeated.

To actually do this, you need an objective measure that is repeatable over many different kinds of products, domains and people and they is a very hard problem no one has cracked. Career ladders and some calibrations help to do this but it'd never perfect and people slip through the cracks.

If you're at a big company, you've seen people get a rating that seemed misaligned to their work because an arbitrary curve is enforced or a project has high visibility by sheet luck because an exec was adamant that the project be on the roadmap.