This is technically not a "bad" measure of performance, but the real danger is the word "competence." Imagine I am hiring two candidates, one has log(n) (level 3) competence across these charts, while the other has very mediocre/poor competence. What if I am working on an application is not performance-critical? What if the "incompetent" guy/girl works twice as fast, because he does not worry about crafting coding-works-of-art? What if the "incompetent" guy is three times cheaper to hire, and eager to prove him/herself, thus putting in extra hours voluntarily? What if I am hiring for a problem with a very specific domain, and expertise is required in only one area?