I don't keep statistics on how many of my games are half pointers, I guess few if any amateurs do. I could look at my online game results, but those usually not "serious" games. I just know that I'm not surprised by half point games - they are not particularly rare. What does interest and amuse me is how often bloodthirsty games, with massive death all round, still end up as half point games. I just have the feeling that if you're evenly matched, your mistakes are going to more or less cancel out, so very close games should not be unusual.

I know that dame strategy is not always relevant, I'm just saying losing won games because of not knowing the correct technique would be a shame. Admittedly we *only* play Japanese rules and counting here in South Africa, so the difficulty or relevance of knowing these dame techniques is only of academic interest.

Right. And since a dame won by a player is lost by the other, 1.5 point-games may also be concerned :



No prisoners.
Japanese rules, komi 6.5 : White looses by 1.5 points.
AGA rules, komi 7.5 : if White connects the ko, she looses by 1.5 points, if she takes the dame, she wins by half a point. White E9, F5, B9, A8, E5, pass, F5, pass, pass

Wow! Thanks you the detailed replies. If only all threads could be so richly endowed

I know exactly what Japanese, Chinese, and AGA rules are. What I said above is still correct. I only play AGA rules once every few years at US Open. Our local tournaments are run with Japanese rules (with one minor modification I don't like and won't get into here).

This example illustrates the fact that it is very difficult to construct a position such that there is no sequence of play that is best under both area scoring and territory scoring that counts points for eyes in seki and one-sided dame. The obvious play by White under territory scoring may be to fill the ko, but filling the dame is also correct.

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I record almost all my tournament games. My results are:

So that's 1 half pointer in my last 76 games. Now perhaps I'm atypical in that at a lot of the smaller UK tournaments I go to I'm the strongest player by over a stone so perhaps not so many of these games are truly even (73% win rate). The half pointer there was against a 4d at the EGC. My previous half pointer was at the London Open against another 4d. I don't play many 4ds (18 of the 76 in fact were called 4d which is quite close to the 1 in 20 figure!).

While the annual US Go Congress officially uses AGA rules, I think some, if not many players still quietly play using informal Japanese rules, and a few may even refuse to pass stones on principle (but more likely out of ignorance).

I don't how many other club-based, AGA sponsored tournaments throughout the country require AGA rules, but AGA rules are not required in order to submit tournament results to the AGA rating database. Oren is right about the Seattle Go Center for example, they officially use a form of Japanese rules for their monthly and other AGA rated tournaments (not AGA rules).

Years ago, the one-day, 4-round Die Hard tournament used to be run using Chinese rules, in an attempt to force people to learn Chinese counting. Its where I first learned how to do Chinese scoring. But I think they only use AGA rules now. Not sure.

Also, way back when we were getting Ing sponsorship/funding, the Ing/NAMT/Masters tournaments were run using Ing rules, but now we only use AGA rules I think.

Still, during some Congresses, there is often confusion with close games on the top tables where the players aren't native English speakers and don't know anything about AGA rules. They just play "Go". Which can be confusing when one opponent is Chinese, the other is Korean, and the game has an odd seki and the score is a half point game (actual game, 2 years ago, I think. I forget who won, but it involved the TD).
Speaking with a number of Strong players afterwards (who were still confused by the rules differences), they typically don't let these rule differences affect their game strategy anyway.

My first US Go Congress a number of years ago, one of my volunteer duties was cleaning up the main playing room every day, which included counting all the stones (which is very easy to do with those special Ing bowls, which I like), and the counting was most important for the Ing tournament games. But I'm not sure if anyone actually noticed.