2021 Rating and rank adjustments

[gennan]

@_KoBa

Like gennan posted earlier this thread, EGF is in the process of updating its ranking system too. According the graph in post 59, it seems like EGF and OGS ranks should align really well in kyu-ranges after their update, so maybe it’s the AGA which should be updated next xD

The graph (reposted below) shows that the Elo width per rank of adjusted EGF and adjusted OGS ranks is very similar in the 20k-5k range (about 50 Elo per rank). So the Elo distance between 20k and 5k will be similar in EGF and OGS (resp. ~700 Elo and ~600 Elo).
Above 5k, the adjusted EGF ranks are a bit wider, so the Elo distance between adjusted EGF 5k and EGF 1d is bigger than the Elo distance between OGS 5k and OGS 1d. But again, the difference is not that big (resp. ~350 Elo and ~300 Elo).

Since the OGS adjustment, I have seen examples where it seems to have resulted in kyu ratings that are much higher than what will be the result of the EGF rating adjustment. But this is only anecdotal. I don’t know if the OGS rating adjustment really inflated OGS kyu ranks compared to EGF/KGS/AGA kyu ranks.

If the OGS adjustment really caused a kyu rank inflation, I’m guessing that the handicap analysis used for the adjustment might play a role. I did note that there is a differerence in how OGS and EGF handle handicaps in rating calculations. OGS doesn’t correct for ½ stone handicap deficit in traditional handicaps. See specifically my post 370 in this thread, where I gave an example for how this could affect the calculation of Elo widths of ranks (and thus how ranks are extrapolated downwards from the 1d anchor):

@gennan

The expected winrate with (H-0.5) depends on the level of the player. It should correspond to the winrate calculated from about half the rank Elo width around the player’s level.

So in the 1d/lower dan range, where the rank Elo width is about 100, black’s expected winrate should be about 43% in a 1 handicap game (½ rank = 50 Elo ~ 43%) between players separated by 1 rank.

But around 15k, the rank Elo width is only about 50, so black’s expected winrate would be about 46% (½ rank = 25 Elo ~ 46%).So for black to win only 43% of 1 handicap games around 15k, the players should be 50 Elo apart after correcting for the ½ rank handicap. So the players should be separated by 1½ ranks, not 1 rank.

So if black has 43% winrate in a 1 handicap game against a white 15k, you might conclude that black should be ranked 16k, but I would argue that black should be ranked 16.5k.

But I don’t know if this has anything to do with anything. I’m mostly guessing here. And the resulting Elo gap between adjusted OGS 1d and OGS 20k (~900 Elo) seems quite close to the same gap in the adjusted EGF system (~1050 Elo), so I cannot really explain how the adjusted OGS kyu ranks can be inflated by more than about 3 ranks at 20k, compared to adjusted EGF kyu ranks.