Vietnam rankings

What the Field column means

Two columns Elo alone cannot give you. Field is the average rating of the opponents a player actually faced, with how many entrants their events had on average: the same score can be built grinding eight-player events against unrated opposition, or playing 200-player regionals. When the field stays around 1500 or events run under 16 entrants, the number is flagged. vs top 5% answers the same question match by match: how many they won against the 2,503 players rated above 1700. The gap is stark — some sit at 59%, others with a higher Elo sit at 30%. Computing these takes the full entry list of every event plus a rating system: sites that start from decklists cannot.

What the ± next to the rating means

It is the uncertainty of our estimate, and it has two causes. The first is statistical: with few matches the number is a guess, with hundreds it is a measurement — the standard error goes from ±60 at thirty matches to ±13 at seven hundred. The second is time: a player's real strength changes, so a rating that has not moved in six months is worth less than yesterday's, even with the same number of matches. The two add in quadrature. A wide margin on someone with many matches means they have not played in a long time. It is not Glicko-2's RD — we use Elo, and this is the error of our own estimate, which is what we can honestly say.