Paar | Contract | Res. | Score | XIMPS | ||
NZ | OW | NZ | OW | |||
1 | 3 NT | C | +600 | -1 | ||
2 | - 1 - | -600 | +1 | |||
3 | 3 NT | C | +600 | -1 | ||
4 | - 3 - | -600 | +1 | |||
5 | 3 NT | C | +600 | -1 | ||
6 | - 5 - | -600 | +1 | |||
7 | 3 NT | +1 | +630 | +4 | ||
8 | - 7 - | -630 | -4 | |||
9 | 3 NT | C | +600 | -1 | ||
10 | - 9 - | -600 | +1 |
Let us consider the example we used before. In a contest of 10 pairs the contract is 3NT at all tables. Everyone
just makes this contract, except one pair who make an overtrick. At MP's this meant a top (8 MP, and a 0 for the
opponents.
At cross-IMPs there are 4 scores to compare with, each of them yielding 1 IMP, for a total score 4 for
the pair who managed to get an overtrick, and -4 for their opponents.
At the other tables all pairs score +1 or -1 IMP. Pairs who play in the same compass direction as the one strong pair
score -1, 1/4 of the score of the pair who had a direct encounter with the strong pair.
You probably have already identified the number 4 (i.e. the number of comparisons on which the cross-IMP score is based) as h, half a top at MP-scoring, or, the number of times - 1 the hand is played. Again we notice that the effect of a direct encounter is h times as large as playing in the same compass direction. This is equally true whether the difference is one trick, as in this example, or whether we have a swing hand where both sides can make game. Also, it does not matter whether or not the Cross-IMP score is calculated as an average, i.e. the XIMPS we used here divided by the number of times a hand is played. In all cases we have:
Also in cross-IMPs playing once against an opponent is equivalent to h times playing in the same compass direction. The techniques we used to obtain an optimal balance are also valid for cross-IMPs.
Conclusion: For cross-IMPs just use the same movements as for MP's.