Defence to 3♠, part III

One of the negative points of using 3NT as a takeout double shape is that when partner passes it (with a few values, no long heart suit and a decent spade stopper) you will often wrong-side the contract. The preemptor's partner is now on lead and can play a spade through the stopper at trick one. This could be expensive, but how expensive?

Today's simulation gives East the same hands he held before. South holds a takeout double hand, about 13+ points with spade shortage and some support for the unbid suits. And North holds a decent spade stopper (KJx or better), 0-3 hearts and no 7 card minor.

This isn't the most wonderful bit of modelling in the world ever, but it doesn't matter much. We're comparing the times when we make 3NT as North with the times when we make it as South. A few deals will slip through where 3NT isn't a realistic contract but it's unlikely that which hand plays it makes much of a difference in these cases.

Over 10,000 deals there were 285 occasions where 3NT made by North but not by South and, interestingly, 193 occasions where 3NT made by South but not by North. On the other 95% of boards, 3NT made from both hands or it went off from both hands.

In terms of IMPs, we lose 0.075 IMPs/board by playing from the South hand.

I must admit that I am a little surprised at these findings and had expected something a fair bit higher, but perhaps I shouldn't have. After all, why should partner's stoppers always be positional? Why shouldn't he be able to duck enough rounds to cut off the preemptor anyway? Here's one of the deals we looked at:

          S: AQ4
          H: KT4
          D: QT6
          C: KJ76
 S: 76             S: KJT9853
 H: QJ6            H: 95
 D: K9753          D: J8
 C: 843            C: 52
          S: 2
          H: A8732
          D: A42
          C: AQT9

Obviously the play is much more comfortable when you have two spade stoppers instead of one, but you'll make 3NT easily enough from either hand. East might have one of the red suit guards, of course, but then you can still make it by guessing which. I'm not suggesting that in any way we're happy to play this contract from the South hand rather than the North hand, just that if we do it's not the end of the world.

So there you have it — wrong-siding 3NT contracts when an opponent has preempted is nothing like as costly as you might have thought.