Life In 19x19

It also seems that on KGS, some players can achieve 9 dan ratings by playing lots of high handicap blitz games against weaker players, but can't hold that rating in even games against other top players.

It's an interesting dynamic. If Iyama is over-rated, I suspect the mechanism is this:

Most games are played in country, so we'd expect the most significant sorting to occur in country. This would be especially true in Japan with more high-purse tournaments and so a larger average weight to Japan-Japan games. A rising star will "steal" most of his points from countrymen.

Internationally, the sorting should tend to be strongest in the upper echelons of players. They last longer in international tournaments, getting more games and more high weight, late round games.

Those combine to make top echelon players significant points of score diffusion. If a new player is added to each country and one is stronger than the other, then the differential is going to tend to flow through the top players to equalize the two new players. Players from the stronger pool will tend to be slightly underrated, players in the weaker pool will tend to be slightly overrated for this diffusion to occur. So if the average new Korean and Chinese professional is stronger than the average new Japanese professional, it would make sense for Iyama to experience some overrating.

That said, there are at least two possible contravening factors. First, flow also occurs with changes in relative strength between pools as well. So if, say, Japanese players are weaker than Korean players, but the difference were diminishing, Iyama would experience some rating deflation. If the gap were growing, that would inflate him.

Second, this assumes that the highest weight international games are between top players. In many systems new players get a big weight boost to all their games to facilitate them quickly getting to the appropriate level. If that's so in this system, and if new players play a meaningful number of international games, the surface area between the pools would be much larger, and there would be no players on diffusion hotspots, so the rankings would be much more accurate in general.

EdLee wrote:There is a video on WeiQiTV from the recent 58th European Go Congress (only ~2 weeks ago).
A top Chinese pro (Liu Xing) gave a European high dan 3 stones, 10-second blitz.
Liu Xing won (twice). The other board is another Chinese pro vs. another
European high dan, same settings. Later, a top Chinese woman pro gave 2 stones.
The Chinese pros won all the blitz games on this video.

That sounds like fun. Does WeiQiTV allow views/purchase of individual videos (like BadukTV) or must one have general subscriptions? Do you have a link?

happysocks wrote:

EdLee wrote:There is a video on WeiQiTV from the recent 58th European Go Congress (only ~2 weeks ago).
A top Chinese pro (Liu Xing) gave a European high dan 3 stones, 10-second blitz.
Liu Xing won (twice). The other board is another Chinese pro vs. another
European high dan, same settings. Later, a top Chinese woman pro gave 2 stones.
The Chinese pros won all the blitz games on this video.

That sounds like fun. Does WeiQiTV allow views/purchase of individual videos (like BadukTV) or must one have general subscriptions? Do you have a link?

http://weiqitv.com/index/live_back?vide ... 6d4d8b4567
It should be this one.
Currently no registration or purchase or subscription is needed for watching videos at WeiQiTV.

Very cool, thank you. Am eager to view more of their videos.

Wow, those aren't just any high Dans, those are two of the strongest players in the whole of Europe. One is an EGF 7 dan, strong enough to be a pro, who used to be an yuengsueng,, the other is an EGF 6 Dan and also EGF pro... 3 stones is still a relatively unchallenging game for the top pro? XO strong