Does anybody know how the ELO system used by yahoo correlates to the ranking system used by KGS?

Don't expect any correlation. It's not a very good place to play go online, unless it's for some reason your only option.

Yeah, I sort've imagine that there's a fairly sharp level cap among the players there. Basically, anyone stronger than about 1d would have both the knowledge and the sense to play elsewhere...

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Tactics yes, Tact no...

I agree with the other two posters that the best answer to the question of "How does Yahoo's rank correlate to KGS's?" is probably "poorly." That said I wouldn't be so quick to discount the potential strength of yahoo players...it is a mixed bag, and you can't always be quite sure how strong your opponent is, but I have played people on that server who are likely up into the mid-dan range or higher on yahoo. Yahoo's system is a bit tough to characterize as (last I knew of) they allowed games on boards of 9x9, 13x13, and 19x19 all to be considered under the same rank, they allowed players to be in multiple games at once, etc. Also they would have people playing against their own accounts to artificially boost ranks (though from what I saw I don't think this shouldn't be an issue since I never saw those players play a game against anyone else). The best way to get a rough guess of a player's strength on yahoo is to look at their game history: If they have a rank that appears strong, and they are 44-1, there's a good chance they are a reasonably strong player. I do think that yahoo provides an interesting experiment for players who are used to more typical" go servers, since they have to try and judge the strength of their opponent based on the quality of their moves, as opposed to the number by their name (=