I do have to say - I think that your estimate is extremely low - I think that between 15 and 25% of the posters are more than just posers, but people who when speaking I would listen to, and 75% of the returning posters are techs, if not higher.

It is very difficult to tell, as there are many, many one time callers who register, ask a question or two and never come back that throw the numbers off, however you do get to recognise the same "efaces" after a while and most of our retun posters are techs.