CUSS
CUSS (CUmulative Sum of Scores) is a possible tie breaker in McMahon Pairing or Swiss System tournaments and is calculated as the sum of the scores a player had after each round of the tournament.
CUSS is approximating the expected SOS of a player.
Example (three rounds):
A player won his first game but lost the second and the third, then his CUSS is 3 points (1 point after the first round + 1 point after the second round + 1 point after the third round = 3).
A player lost the first two rounds but won the third round, then his CUSS is 1 point (0 points after the first round + 0 points after the second round + 1 point after the third round = 1).
A player won all three rounds, then his CUSS is 6 points (1 point after the first round + 2 points after the second round + 3 points after the third round = 6).
Historical note:
Several years ago CUSS was in use at EGF tournaments for a short period to eliminate the possibility of a player affecting the SOS of his opponents by intentional losing all is following games in order to reduce the chances of his opponents to finish at a good place. Why should he do so? Because he has a friend who has chances to finish at a good place too - and earn some prize money.
Drawbacks of CUSS:
CUSS is not used in any tournaments any more. It's because it does not really reflect the average strength of the opponents. With CUSS playing a weak opponent in early rounds of the tournament means an easy win without the drawback of getting bad SOS. The influence of the draw is too big to be acceptable.