Assesing exact numbers would be difficult as that would involve some criteria as to what is a 'real dom' and what is a 'real sub'. Maybe putting together a questionaire to ask certain leading questions may help. i.e. rather than ask 'are you a real dom?' which will get the immediate 'yes' answer from many, including players and abusers, you need to consider questions that indicate the psychology of a true sub or Dom. Simple ones like 'how much real life experience have you had' can be asked as can more subtle ones like 'Your sub refuses to follow your direct command. Do you a) punish her severely by slapping her in the face b) tell her that she has lost some priveleges and that you will talk to her about this afterwards c).... etc. In this question I have a feeling that a) is an answer an abuser/wanabee would give while b) is more of a true Dom answer (though I am sure some of the Doms on here can give better options). Even more subtle psychological profile questions could also be added to this.

Of course a questionaire like this would be difficult to set up and require a proper psychologist to write along with at least one 'true sub' and one 'true dom' to act as baselines ... And, of course, how does one define a 'true' anything in the scene?