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Imp Strategy

In a team game you and your partner sit N/S at one table, and the other pair of your team sits E/W at the other table.  In team game scoring your score on a board is added to your teammates score on the same board and coverted to International Match Points (IMPs) using this scale:

0 - 10 = 0           220 - 260 = 6       600 - 740 = 12      1750 - 1990 = 18
20 - 40 = 1         270 - 310 = 7       750 - 890 = 13      2000 - 2240 = 19
50 - 80 = 2         320 - 360 = 8       900 - 1090 = 14    2250 - 2490 = 20
90 - 120 = 3       370 - 420 = 9     1100 - 1290 = 15    2500 - 2990 = 21
130 - 160 = 4     430 - 490 = 10   1300 - 1490 = 16    3000 - 3490 = 22
170 - 210 = 5     500 - 590 = 11   1500 - 1740 = 17    3500 - 3990 = 23
4000 & over = 24

For example suppose you played in 4H non-vul and made it for +420 and your partners at the other table defended 3H making 4 for -170.  We add the 2 scores 420 + (-170) = +250 which on the scale is +6 imps. We gain 6 imps on this hand, and the opponents lose 6 imps. Now for how this affects our strategy:

BIDDING

1. Part scores

Strive to get a plus score. Lets consider the situation where we are bidding spades and opponents clubs and the opponents push the auction to 3C. Our problem is whether we should defend 3C or bid 3S. The other table will have the same problem so we must consider the possibility that one table bids 3S and the other defends 3C:

  Our table   Their table
- 3S makes 3C makes +140 + (+110) = +250 = 6 imps
- 3S makes 3C down1 +140 + (- 50) = + 90 = 3 imps
- 3C down1 3S makes + 50 + (-140) = - 90 = -3 imps
- 3C down1 3S down1 + 50 + (+ 50) = +100 = 3 imps

- 3S down1 3C makes - 50 + (+110) = + 90 = 3 imps
- 3S down1 3C down1 - 50 + ( -50) = -100 = -3 imps
- 3C makes 3S makes -110 + (-140) = -250 = -6 imps
- 3C makes 3S down1 -110 + (+ 50) = - 90 = -3 imps

Notice that when our table is plus (first 4 examples) we win imps in 3 cases out of 4. When our table is minus (last 4 examples) we lose imps in 3 cases out of 4.  The same is true for our partners at the other table (when they were plus we won imps 3 times out of 4).

Principle:  Your part score bidding should aim to 
create a plus score, the size of the plus not being that important.

 

2. Games

When vulnerable try your best to get to game. It goes 1S-3S limit from partner, and you hold a minimum type hand.  Should we bid the game? Let us consider one table in 3S, the other in 4S.

   Our table  Their table

- 4S makes 3S make4 +620 + (-170) = +450 = +10 imps
- 4S down1 3S makes -100 + (-140) = -240 = - 6 imps

If the game depended on a finesse (50%) then we would expect to gain 2 imps per hand by bidding the game when vul. We should actually be in all vul games that are 37.5% or better (3/8, 3 times we win 10 imps, 5 times we lose 6 imps). It is impossible to judge this percentage in the bidding, so we just stretch as hard as we can to bid any vul game which may have a chance.

Principle:  Be agressive when bidding Vulnerable games

Compare this with not vul.

- 4S makes 3S make4 +420 + (-170) = +250 = + 6 imps
- 4S down1 3S makes -50 + (-140) = -190 = - 5 imps

Here its just about even/Steven so we should only bid games which are about 50%, or in other words bid normally and only accept invitations if you think its right

 Principle:  Bid normally when bidding Non-Vulnerable games

 

3. Small Slams:

Whether vul or not, only bid slams that are 50% or better.

VUL

- 6S makes 5S make6 +1430 + (-680) = +750 = +13 imps
- 6S down1 5S makes - 100 + (-650) = -750 = -13 imps

NOT VUL

- 6S makes 5S make6 + 908 + (-480) = +500 = 11 imps
- 6S down1 5S makes - 100 + (-450) = -550 = -11 imps

 Principle:  Bid normally when bidding small slams

4. Grand Slams

Don't bid grand slams unless you are reasonably sure they are making

VUL

- 7S makes 6S make7 +2210 + (-1460) = + 750 = +13 imps
- 7S down1 6S makes - 100 + (-1430) = -1530 = -17 imps

NOT VUL

- 7S makes 6S make7 +1510 + (-1010) = +500 = +11 imps
- 7S down1 6S makes - 50 + (- 980) = -1030 = -14 imps

Since you stand to lose more when a grand goes down then you will gain when it makes, you want to be fairly certain it is making. (Vul 17/30 = 57%, NV 14/25= 56 %)

Principle:  Be VERY conservative when bidding grand slams


5. Sacrificing

Lets assume we are contemplating a 5C sacrifice over 4S  We examine some score comparisons

NV vs VUL (favorable)

- 5cx down3 4S makes -500 + (+620) = +120 = 4 imps
- 5cx down3 4s down1 -500 + (-100) = -600 = -12 imps

- 5cx down2 4S makes -300 + (+620) = +320 = 8 imps
- 5cx down2 4s down1 -300 + (-100) = -400 = - 9 imps

If you judge the sacrifice will go 2 down then your potential gain of 8 imps is about equal to the potential loss of 9 imps when their game wasn't making.  When you judge it will go 3 down however, you only stand to gain 4 imps, but lose 12 if 4S wasn't making. And remember that when vul, we stretch to bid those 40% games. In this case its probably best to pass and defend.

Principle: At favorable vulnerability sacrifice only when down 2 at the most.
                 Be conservative about sacrificing
                

                 At equal or unfavorable vulnerability you should be bidding to make
                 your contract, NOT as a sacrifice.

Conversely, when the opponents sacrifice against your 4S contract, if you have stretched your values at all to get to game you should be delighted to double. Even if you haven't stretched, double will be preferred more often than not, as it is better to potentially lose 4 imps than lose 12 imps by bidding on and going down

Principle:  When the opponents take a sacrifice you should double 
                  
if there is ANY doubt you might not make your game
                 
contract if you bid on.

 

DECLARER PLAY

Since overtricks are worth only 1 imp and going down in a game contract can cost 10-12 imps, we play as safely as possible to make our contracts and pay little attention to overtricks

 

DEFENCE

Again, since overtricks are worth little, the object of the defenders play is to beat the contract