This might kind of seem harsh, but I think it takes into account that there's a lot of knowledge to have in most subjects, and most people take very high levels of knowlege for granted. When I recruit, and when I train people on hiring, I propose a very curious rating on a zero to ten scale:
Zero. don't know how to spell it
- heard of it
- wandering around the bookstore to find a book on it
- did some tutorials, half a clue
- used it a bit
- familiar with most stuff about it
- did a very substantial project with it
- multiple substantial projects with it; expert on my team
- expert at my company, or my region; contributed to the technology
- world expert that contributes to the technology world-wide; wrote or managed an implementation of this technology
- standards committe, inventor, owner of the technology
Most people are surprised at this because they rarely see experts who are better than 5 or so. They just don't think such peopl exist. But if you're hiring world-class talent, a big part of your team might be made up of people who are 7 or better on that scale.
Consider the sphere of influence of these levels:
Zero. None.
- None to self.
- Self.
- Self.
- Self.
- Self to team.
- Team to project.
- Projects to division/org.
- division to company. Maybe starting to influence outside.
- world-wide.
- World-wide.
Not a ton of teams need people who level 8 or more. But certainly almost every company needs someone who's level 7 or more -- or at least has the potential to become that kind of contributor.