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 Post subject: KGS Sudden Rating Jumps
Post #1 Posted: Thu Jul 08, 2021 12:55 pm 
Judan

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I saw sudden, large rating jumps for some other people's accounts. My own account (sum) did not have them; it was only affected by global rating resettings. Now, suddenly my account has also been affected as follows:

1) I played some rated games to 2021-05-19.
2) To ca. 2021-06-30, the rating remained rather constant while I did not play rated games.
3) On ca. 2021-07-01 to 2021-07-03, my rating increased by ca. 0.58 ranks.
4) On 2021-07-04, I won one game. My rating increased by ca. 0.23 ranks to the next day.

The sudden large rating jump (3) makes no sense whatsoever. Trying to justify it by meticulous analysis of all rating data would not provide any practical sense. If the games played in (1) shall cause a large rating increment, this should occur sooner rather than later and gradually rather than sudden. The actual rating behaviour (3) amounts to the rating strategy "It is best to NOT play and wait for the rating to increase much". Not playing ought never to have a very much more positive effect on a player's rating than playing and winning.

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 Post subject: Re: KGS Sudden Rating Jumps
Post #2 Posted: Thu Jul 08, 2021 11:10 pm 
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My latest rated game was on May 26 and my rating curve has been almost flat since then.

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 Post subject: Re: KGS Sudden Rating Jumps
Post #3 Posted: Fri Jul 09, 2021 11:47 am 
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I can see two reasons for the shift, and I suspect a combination of both.

The KGS rating system uses historical games that go back 90 days. The big shift in your rating started late June. Looking back 90 days from there, you had about 30 rated games on record. 23 of those games were played on March 20-21. After 90 days pass a relatively large proportion of data drops out of the ratings window. The old game results aren't there to help pin down your rating and new games will have a larger impact than before.

In that period you also got promoted from 3d to 4d. Ranks become "sticky" close to a promotion because of the handicaps. Playing against a 3d, a 3.9d player will have komi while a 4.1d won't, and a win will have a much greater benefit for the player just across the 4d boundary. The games that vanished in March were those you played as a 3d.

Once the March games vanished from the ratings window your game record was 4-1-2 playing as a 4d, and then you show up again in July with another win. Certainly the record is consistent with a rating much better than a 4d on the cusp of demotion, and was adjusted accordingly.

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 Post subject: Re: KGS Sudden Rating Jumps
Post #4 Posted: Fri Jul 09, 2021 2:02 pm 
Judan

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It was 180 days; 90 days eases things a bit. However, it remains a mistake trying to improve much by playing a lot regularly; doing so keeps rating increments hard. It is much easier to not play and wait (not my intention but working hard is the tesuji for having little time to play and therefore profiting from larger rating volatility accidentally).

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