I don't think that's something you could even count. There's no ticket to enter the complex, only an event. And then you couldn't get a count of someone going to say, a RunDisney Expo (just as one example) as there is no tickets or anything used to enter it
As to how many attend events at the complex, I don't think you'll get a count on that either. Even if Disney had the number, they don't share it.
And I'm not sure Disney even puts on all the events themselves. I believe some are done by 3rd parties that rent the facilities (but not certain on that)