Ah. Let's change tactics, then. Forget the million people out of 50 million (admitted nonsense).
The number of people who have bought D&D is objectively significant TO ME. Because I feed my children by selling comic books and D&D, and I've been selling Starter Sets (and Core books, to a lesser extent) to a not-insignificant number of people who SAY that they are there due to ST.
How that translates to the rest of the world? Who knows for sure, but I usually find (when talking to other retailers places like ComicsPRO meetings) that my experience is usually repeated in my across the world.
So it's significant to ME, and I can say confidently to US (when referring to other game retailers). We are the very definition of "small", of course. But not insignificant, I hope you'll agree.