When are we regarded as experts? I know this is an unanswerable question because it is largely in the eye of the beholder, but I wonder about the common notions of expertise.
As an author, I always chuckle because it does seem to be the case that many people regard me as an expert because I wrote about something. There are certainly many authors who don't know diddly. There are likely people who don't think I know diddly. So writing about a topic does not really equate to being an expert. What if someone blogs about one topic every day - does that make him or her and expert? Most would not put that on the same level as writing a book, but I can tell you that maintaining a blog requires more thought and work in a year than writing a book.
Some people say that a degree gives us expertise. That argument is a bit suspect too, especially when it comes to crafts that are relational, like management and leadership. And we all have known MBAs who could not management themselves out of a tight corner. A degree does not necessarily equate to expertise (perhaps lengthy scientific degrees would be the exception).
Perhaps time with a discipline builds expertise. This might be the case, but I don't think is it necessarily the case. Some managers never become experts and others lose their expertise because they do not stay current. This assumption depends on the mentors one has had and whether they have stayed current in their field.
Some people say that you are an expert when someone will pay you for your knowledge. So the minute you can consult on a topic renders you an expert. Again, like all professions, some consultants know their stuff and others peddle snake oil.
Who gets to say one is an expert? Can I claim my expertise or am I only an expert if others acknowledge me as such? Perhaps the answer is, "whichever works for you." Confused?
I occurs to me that when we see ourselves as experts we are more likely to be actively engaged in our discipline. So if regarding yourself as an expert helps you stay current, I say, "go for it! It is all semantics anyways, right? Our beliefs should serve our goals and enable us to optimally contribute. What's real, true, or validated is often unknowable and of no consequence.
Expertise is a made up conversation. But then, most of our conversations are made up.