In our case is a very small percentage, not getting to 1% of total registered users, for the time being, from a total 90K+ users. This 1% is really powerful and trusted experts in their subjects for the rest of the community. Most of the discussions in the forums are technical question that require an answer that is not always so easy or at least, takes some time to explain.
These users are definitely making grow our community by contributing there, and they are worth being followed. My opinion is that just having a handful of people with knowledge on the topics covered by the community will spread the word enough as to attract more users and encourage others helping out.
Thanks Miguel. Very helpful.