Word of mouth, I suppose? Only Shardbearers participate, but everyone else knows something is going on.

[ he sets his plate down and dusts off his hands, but he's content to keep drinking while he talks. ]

In their defence, keeping records might be pointless anyway. I've also been told that the Oracles have a will of their own. They correspond to the Aspects we all fall into, and no one knows what makes them choose one side over the other. We're being graded on unknown criteria.

So! That's why it's complicated.