Since this is really data about the person I would like it to also be available on the person's profile page. Perhaps in the section containing their personal data.
To answer the question and to add to Jeff's post...
To keep the inevitable support questions like "My calculated rate is wrong" or "What does this percentage mean?" to a minimum, the profile could contain the information which is used to calculate that number.
- Number of questions not community wiki
- Questions older than 3 days.
Questions with at least 1 answer.
...plus # of qualifying questions with an accepted answer = %accepted.