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No, not yet and I don't think it would matter that much. As comparing users to pages, on steemit, only a very small amount of users (let's say 500k) compared to pages on the web (a lot more) exist. Computationally it doesn't currently seem to be a problem, so optimizing it would bring little added value. And also, the total follower graph doesn't change drastically daily: a lot of new relationships may be formed and some (a lot less) are terminated, yet all in all that wouldn't make a big difference to the overall end-results. So daily re-calculating the UA binary index (containing about 8 bytes per user, or more if more information is stored in it), is fine.