Dear chess.com community,

I noticed that when playing rated Online Chess games with chess.com the ratings adjustments are calculated using present rating scores rather than the ratings held at the time of beginning the match.

i.e. A game begins between a player rated 900 and a player of 1400 rating but during the days/weeks it takes to complete the game both players' ratings change. Player A, who was rated at 900 is now rated at 1400 whilst Player B, who has a rating of 1400 is now rated at 1300.

If player A goes on to win the match they win few points, but may lose many points, even though Player A was of a much lower rating when the game started.

Is this a bug, or is there a legitimate reason why gaining/losing points in other games affects the rating ratios of games that take a long time to complete?

As the game progresses the ratings of the players get constantly updated. So yes, the rating adjustment will be based on the most recent ratings which makes sense.

Except that if you took a bet at 5/1 it would still be honoured at 5/1 regardless if further odds changed it to 10/1 or 2/1.... Spurious analogy, I know, but one must understand the logic.

You said it all: "Spurious analogy".

Let me give you a different one to better carry across the concept of rating someone based on his most recent playing strength rather than the one when the game started.

Let's say you go to the doctor and get a health check because you want to go on a climbing expedition to Mount Everest. Everything is fine. Six weeks later you arrive at Everett Base Camp and you feel miserable. Should the expedition leader make his decision whether he let's you go up the mountain based on the health check you received six weeks prior or what condition you are in at that moment?

As for your bets example you do realize that while a bet that you make at any given time won't change (because you finalized the transaction) the odds will constantly update getting closer to the event reflecting the change in likelihood that a certain outcome will occur. This is exactly the same as in chess. Once you get a decisive result your rating (bet) will be fixed at that point. As long as the outcome is still open your rating (odds) will fluctuate according to your most recent strength.

Also if you are a fairly new player then it is likely that any changes in your rating are likely to be a more accurate figure as the system gets to know more about you based on the more games you play. So the later result should tend to be the fairer rating.

I take it you don't gamble on sporting events much, because this is generally not the case. The odds change based entirely on bets that have been placed, and the odds are fixed after all betting has ended. A readily available example is horse racing, where you can watch the tote board and see the odds fluctuating right up until post time. When you win, the bet is paid according to the FINAL odds, not the odds at the time the bet was placed.

But back to your original question: Over a large number of games, whether you use the ratings at game start or at the time the game is completed, your rating would approach the same value. In any case, I'm fairly certain that it's not a bug. It works the same way in correspondence chess: When you finish a game that stared months ago, your rating change is calculated based upon your current rating at the time the game is completed, the same way it is done here.

rightly   said 

Regarding the betting analogy, if somebody takes a bet at 10/1 their price remains at 10/1 regardless of further bets changing future betting prices for later customers.

That's not true, you are paid dependant on the odds given at the time.

The reason I don't like it is this:

Say a 1400 plays a 1200. The 1400 stays at the same level but the 1200 improves over the course of a few months it may take a game to complete. Therefore their rating increases to 1600 for example but the initial moves they played may have been of a 1200 level, giving the 1400 a winning advantage against someone who is now rated 1600.

Exactly.

Not sure if trolling, or just... you know the rest.

You are absolutely wrong. I don't gamble much, but I play the ponies from time to time; more than enough to understand the payout structure. Try refuting the individual points next time; you might get some mileage that way.

In any case, if an experienced (i.e., more than 200 fairly recent completed games) 1400 defeats a 1600, his rating will only be two or three points higher than if he defeats a 1200. I know that people are stupid-protective of their ratings here, but come on... all this over the difference between a 1409 and a 1412? It self-corrects over time anyway, unless you are trying to nurse a few points by delaying moves in losing games, and even then after about 1000 games it will approach your "true" rating, whatever rating-manipulation games one tries to play.

I don't like the way the ratings adjustments work in Online Chess.

Currently I have an ongoing game against a guy who was rated 1800+ when we started. I got a nice advantage in the position, but the guy dissapeared and started losing all of his online games. His rating now stands at under 1200, so whatever happens is not good for me. If he doesn't return and I win on time, I will get zero rating points. If he does return and we play out the game, and he wins, I stand to lose over 30 rating points, but if I win, his rating will likely still be so low that I will win zero points. Of course, he's really at least an 1800 level player, so the risk/reward is absurd.

Anyway I know that's maybe bad luck, but still I think it's more fair to just lock in the rating of the player at the time of the game. Just my opinion.

Oh by the way, I don't know what kind of bets you guys are taking, but in any sportsbook bet I have ever taken, the odds are locked in at the time of the bet. If I take the Lakers -7 a week before the game, when the game starts I have the Lakers -7, period. It doesn't matter what the current odds are. Who would ever bet if you didn't know what your odds were?

Apples and oranges. As correspondence games can last for a very long time it makes perfect sense that the rating gain/loss will be calculated based on the rating at the end of the game. It is unfortunate that you have to deal with members that time out/lose interest/whatever and have severe rating fluctuations but life ain't perfect. As it only reflects a small number of all your games the net effect on your rating is negligible.