Just an empirical observation, your average karma seems to recalculate on a periodic as opposed to a continual basis. I've noticed at times that, after posting

Just an empirical observation, your average karma seems to recalculate on a periodic as opposed to a continual basis. I've noticed at times that, after posting something that gets a lot of upvotes, checking my profile (even when I don't hit my browser cache) doesn't show any increase to my average, yet waiting a day or so does. This is purely anecdotal and unscientific, but it's a consistent observation.