I don't think you can sum up all the Bot-SP and compare them to all SP left because you also have to consider how active the SP is used. For example take a look at neds SP, he has 1,752,000 SP and he doesn't use them a lot. And I don't know how many accounts don't upvote a single thing.

I would say that the bid bots own far more than 12% of the actively used SP.

Well but not that it's a bad thing ^^