Forgive me if I have missed the info I seek somewhere on the site. Can anyone clarify if the rating calculations are done from the ratings of both players at the start of a game or the ratings of both players at the time of the final move (which obviously can be dramatically different from when the game commenced). I notice that some players stop playing at their regular pace when in an obvious losing endgame, and wondered if this is to try and influence their rating wth the other games they still have in play? I hope that makes sense. Thank you in advance.
The ratings at the time of finish are used. Some people play more slowly when they're losing, because they want to take more time to find the best move. There are always a few exceptions, but I don't encounter those people here often.
I generally play more slowly when I'm losing a game for the simple reason that it's harder for me to find a good move. When I'm ahead it's easier to see a good attack or find a good defense. But when I'm behind in material or position I'm more likely to choose the "skip to next game" option (unless time pressure is forcing me to move) because I can't figure out what to do so I think "I'll give it a fresh look tomorrow."