Joshua Dyal said:
If you don't like my assumptions, fine. But otherwise, I don't see what you've got against them.
I'm going to be long-winded here. Please bear with me.
I start with the note that we actually don't have a quote on Mr. Dancey saying that D&D vastly outsells other games. We both seem to remember such statements, but it is possible we've got it wrong. Specifcally, if the "vastly outsells" is not for the time around the 59%, this whole leg of discussion quickly becomes moot. I will, however, continue as if we are correct, as we both seem to remember it that way.
It isn't a matter of liking or disliking your assumption (though I strongly suspect it doesn't match reality). It's a matter of disliking what you are doing with that assumption. Quite simply, you are practicing very unsound reasoning. When you take into account that the conclusions you reach reflect upon the competence and/or integrity of an individual (Mr. Dancey), then perhaps you'll see how my statements are not at all "petty".
The proper procedure is to form an hypothosis (make an assumption), find relevant data, and use that data to test the assumption. The thing you should not do is form an hypothosis, find a piece of data that neither confirms nor denies the hypothosis, and use them in combination to interpret what another piece of data means, and continue on as if that interpretation were fact. Conclusions based upon unfounded assumptions are themselves unfounded. No matter how reasonable an assuption may seem to you (and, yours does not actually seem more reasonable than the alternative, to me), it is no substitute for fact.
You come to the conclusion that Mr. Dancey's statements (as we remember them) are inaccurate, for whatever reason (dreadful error in speech, incompetence, or lying are your basic options). Given that those statements have apparently stood for years without factual contradiction, I doubt this is a tenable position. Even if it were tenable, you should be reticent to choose among those basic options when your logic is based upon... well, on smoke. There's not a shred of actual evidence that the statement was incorrect.
Simply put - what's more likely: Mr. Dancey is correct, or your conclusion? My money is on Mr. Dancey.
I propose you turn around and use the proper procedure. You have a hypothosis - players of various RPGs all buy similar amounts of materials. Well, if we trust WotC and their representatives (give me a good reson why I shouldn't), then, 59% or more of gamers played D&D, and D&D vastly outsold the competition. The mere 18% lead in sales your assumption predicts is not "vast". Ergo, the assumption is likely faulty, which means that D&D players do in fact buy more books.
That's not at all impossible - D&D has more core rulebooks than other games. D&D has a reputation of attracting "powergamers", who are more likely to buy books for rules reference than a "story-immersion" gamer. D&D has as many if not more "splatbooks" than other games. D&D has a plethora of settings, where most games have one. Heck, the simple fact that D&D uses an elaborate "spellbook" section that players constantly reference may well add to sales.
Why the great resistance to the idea that the assumption was faulty? Is the thought so abhorrent that it must be denied?