Cross-IMP Scoring

New options for the scoring of Swiss Pairs

Two methods to overcome some of the perceived unfairness of a Swiss Pairs competition using Butler datum scoring. In particular, it is thought that datum scoring favours the side that "has the good cards".

Dividing the field into separate NS and EW sides

The field is seeded so that both sides are of equal strength. The Swiss draw is modified so that each pair stays in the same direction for the entire event.

Scoring by Cross IMPs

Cross-IMP scoring with the field mixing NS & EW as usual. "Cross IMPs" means that each pair's score is "imp'd" against every other pair (as opposed to the average score of all other pairs in datum scoring).

You can Google "cross imps scoring bridge" to find much interesting discussion on this topic. Basically, it damps down much of any “wildness”. A typical data sheet would look like this:

(hold down CTRL and roll the scroll wheel on your mouse to zoom in if you can't read it)

Michael /Geo’s 230 on board 13 has been “IMP’d” against all the 25 other scores on this board. It’s not as good as the 620 that EW got at table 1 (means +9 IMPs to Gwyn/Kate) but better than the 110 EW got on table 2 (means -3 to Gwyn/Kate), way better than the 120 NS made on table 3 … etc etc. All these scores are averaged to give an IMP total of 4.4 to Michael/Geo on board 13. This contrasts with “imp-ing” the 230 score against a single datum figure calculated by averaging all eligible raw scores – possibly -90 in this example – to give an IMP score of -4.

You can re-score a set of final results in cross-IMPs. Don’t expect huge upheavals, though. You should allow that, using this slightly fairer way of scoring Swiss Pairs would mean slightly fairer draws throughout an event. This would build until the final placings may well have look quite different to ones run under the Butler datum method.

You can see such a sample event by comparing this with this.