Competence vs. expertise

Hello, it's been a while since my last post. I have been thinking about the differences between competent and expert performance, and wondering how exactly the two are different. I have the general impression that expert performance exceeds competent performance, but I am not clear on the details. How does the expert go beyond competency? Is expertise a collection of super competencies? Are there some situations that you would want expert as opposed to just a competent person? Is there a limit to one and not to the other?

I have often seen lists of competencies that when combined indicate someone has mastered something or gained expertise. Therefore, competency must come before expertise, but I wonder what the time frame is or what level of competency must be reached before you are called an expert. I am going to to back to some of the literature on expertise and see what the "experts" have to say. I will get back to you when I find something of interest. Until then...