pentejr: It depends on who the winner is. The higher rated winner gets less and loses more. Vice versa for the lower rated player. But the two are not balanced and that makes your point substantially correct.

For instance with me, at 2430, against a player at 2150.
I'd go up 2 for a win or drop 13 for a loss. He would lose 3 or gain 23.
Thus the ratings pool loses 1 if I win and gains 10 if I lose.

Given that I'm never going to win 10 : 1 against any player, the rating pool will gradually increase in value from me playing this opponent. The same will happen with other pairings. This supports Alan's theory that the rise in Backgammon and Hypergammon is a result of the number of games played.