What is it all about and why do we do it?
1. How is Cross IMP Pairs scored?
2. What are the advantages?
3. What are the disadvantages?
4. Never mind that, why are we doing it?
5. How should we adjust our game with this sort of scoring?
1. How is Cross IMP Pairs scored?
Your cross IMPs on any particular board are calculated by comparing your score with everyone else who played the board in the same direction as you. The total of these comparisons in IMPs is averaged to give you your cross IMPs on the board.
The cross IMPs for all boards are then added up. The total is adjusted if some pairs played fewer boards then others to bring it in line.
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2. What are the advantages?
a. In Cross IMP scoring you just need to make your contract to get a suitable reward, especially games and slams, making overtricks doesn't gain you much.
b. There is little to choose between 3NT and 4 of a major and the few points difference is almost irrelevant, so you should choose the safer game, the same as if you were playing rubber bridge.
c. At normal pairs scoring (matchpoints), pairs have a natural fear of going past 3NT in search of a minor suit slam. This has the effect of making people's slam bidding rather poor. As 5 of a minor will score OK compared to 3NT at IMP scoring, your slam bidding should improve.
d. Safety plays that risk not getting an overtrick in return for greater safety are a luxury that you (usually) cannot afford at matchpoints. Yet a lot of bridge literature is about this very topic and may well have figured significantly in any lessons on the game you may have taken. It is nice, at least for a change, to have a form of scoring where safety plays may figure more prominently.
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3. What are the disadvantages?
a. Matchpoint bridge is still exciting, with tactics all of its own.
b. Matchpoints are simple to score and simple for everyone to see where their score has come from.
c. At matchpoints, as each board is worth a simple top, bottom or a shade of grey in between, over a limited number of boards (and 24 is limited), you may get a fairer result (fairer in the sense of less random) as each board is worth the same amount. If a good pair comes to your table and bids a slam that the rest of the room has not been able to find, you will get a bottom at matchpoints which may be no fault of your own. This is an unfortunate setback, but because each board is worth the same as every other one, you can potentially recover on the next (perhaps partscore) board. At cross IMP scoring you will need at least two, probably three partscore swings in your favour to make up the lost ground. This is not a concern in the long run (luck will even itself out), but in a single session at cross IMP scoring a few 'big boards' has a bigger effect than at matchpoints.
This is probably the main reason why matchpoints are the norm for pairs scoring for most sessions - though it is not a compelling reason why all sessions should be scored that way.
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4. Never mind that, why are we doing it?
Well, apart from the things listed above as advantages of cross IMP scoring, the actual history goes back to the last Thursday of the month when we had 'multiple teams'. Some did not like teams because they did not like potentially letting their teammates down. Some didn't like them because sometimes moving around the room was complicated and also they didn't know how they were doing as scoring units don't show percentages. Cross IMP pairs seem like an ideal compromise. There are no teammates to let down and moving around the room is like for any pairs event. Our scoring units will show cross IMPs (not percentages) and this gives you an idea how you are doing - 0 cross IMPs is like 50%, any + score is more than 50% and any minus score is less than 50% - roughly.
Additionally, there are those who play team matches outside the club sometimes, but, as nearly all bridge is pairs (and therefore matchpoints), there is actually very little opportunity to practice the tactics required for team matches. Playing at least some sessions of cross IMP pairs provides that opportunity.
Also it is a bit of variety, it is nice to have a different form of competition sometimes in order to try to give something to everyone. Cross IMP pairs is just part of that overall effort.
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5. How should we adjust our game with this sort of scoring?
You could write a book about this, but briefly:
a. When choosing which game to be in, you should choose the safer option.
b. You should not fear being in 5 of a minor so much as you do at matchpoints, especially if you want to investigate the possibility of slam.
c. If you think your side has the majority of the points, but not a game, then if the opponents bid over you, you're in a situation where you will need to think if you should bid one more yourself, double the opponents or just pass. This is a very common situation. Often at matchpoints you should double and pass is commonly the wrong answer. The reason is simple enough - if the opponents can make their contract you're getting a poor score anyway, so the extras they get for making a doubled contract won't hurt you very much, if at all. Whereas an extra 50 or 100 if you can get them off may make quite a difference to your matchpoint score. At cross IMPs the maths is a little different - the extras they get for making a doubled contract, particularly if you double them into game, will hurt you badly. And, if they're off, the extra 50 or 100 won't benefit you very much. In any case, at cross IMPs, if it is a partscore board that your side should be getting a plus for, it will, at least, not be a bad board for you if you collect any sort of plus at all.
d. At matchpoints, if you have a close decision between bidding game or not, then it is generally right to be conservative in your approach. The reason is simple, if the game turns out to be worse than a 50/50 bet then the advantage of staying low is obvious. And if it is a 50/50 bet then, by staying in the partscore, you will still pick up a few matchpoints from those who have got into the wrong denomination (which is more common than one might think), provided, of course, that you don't get too high yourself. At cross IMP scoring the game bonus is worth pursuing especially vulnerable and you should be more aggressive in your game bidding (marginally).
e. At cross IMP scoring generally you should play to ensure your contract as overtricks are of little value. And in defence you should play to get the contract off even if this risks giving away an overtrick.
Modified for Chislehurst from the original article here.
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