My rating went down after a won game??

Can someone explain to me why my rating went down in this game?

https://www.littlegolem.net/jsp/game/game.jsp?gid=2370268

When you play much lower ranked players that happens

Doesn't the Hahn system evaluate not just whether you win or lose, but by how much? As in, a rating advantage of X means that you're expected ot win by Y amount, so if you come in under that you've underperformed and so lose rating points?

The problem of winning against a much weaker player (in a simple win/lose game) lowering your rating exists some places, but I don't think I've ever seen it here.

I do not believe that is the case. It is rational to secure your win safely once you have a lead, so you do not necessarily win by as many points as possible. I know of no system where winning can cost you points. Mathematically it does not make sense. (I am a mathematician.) Over a very long sequence of games between any two players, assuming their strengths do not change, their ranks should not change.

Basically it represents the probability of a win, the weaker player will win once in a while that should bring their ranks back into line.

Doh, wasn't done.

When a game is handicapped, each player should have an equal chance to win, so the ranking change should be constant no matter the ranks. That is something the AGA doesn't get, they grabbed their system straight from the chess system without understanding it.

@Randlph, it was Hahn system where your statement "It is rational to secure your win safely once you have a lead, so you do not necessarily win by as many points as possible" is simpy wrong.

Today, something has changed with the ratings again. But before the changes it was like this: Your rating was 1743 elo, your opponent's rating was 1583.4 elo. Difference=159.6 This means the average expected result = 0.7148. You scored 70% against 30%. I.e. less than expected. Therefore, the rating has decreased.

@richyfourtytwo
Your statement doesn't parse correctly, could you rephrase it and back it up with some real information. I've read the commentaries of many professional games, they frequently play cautiously once they have secured a win.

@Kalabas
So, how does the system work now?

Randolph, you are of course entirely right when talking about Go, Not only professionals do that, even I do it. :-)

But this was a game in the Hahn variant, which is - strictly speaking - not Go. See: https://senseis.xmp.net/?HahnPointingSystem

Ah.

Thanks.

For the Hahn system, it is not the win-loss that is important, but the specific number of points.
You don't get 2 points for winning and 0 for losing.
You get a certain number of points in the range from 0 to 100 depending on the number of captured stones/territory
As I understand it, the result of 70:30 corresponds to 0.7000 in the elo system.

Thanks Kalabas.

I finally figured it out from the website provided.