Does it make sense to double (for penalty) in the following situation?

Question

With only us vulnerable at matchpoints, and after two passes, I bid 1NT (15-17).Partner knows I would not "shade" my values for a 1NT bid in third position as I might with a suit.

The direct seat opponent overcalled two spades, which bought the contract. Partner passed with ♠ K986 ♡ QT ♢T73 ♣ J642. I wasn't about to speak again because partner is "captain" after a 1NT call. (He knows a lot more about my hand than I know about his.) We set the contract one but got a bottom for only scoring 50. We would have gotten an average score for 100.

I said, "I wish you had doubled. Since I have at least 15 high card points, even in third position, you knew that we had the balance of points. We also had close to parity in trumps, because I would not bid 1NT with less than two small ones."* (I actually had 16 high card points and A53 of spades, which I would consider "average expectations" for total and suit strength for a 1NT bid.)

Partner said, "If I had doubled and they had made it, we would have doubled them into game." I agree with him as regards a rubber or "money" game, but not at matchpoints.

Who was more nearly correct (for matchpoints), partner or me?

*Also, I deduct one point (for NT) for a weak doubleton, meaning I would not bid a 15 point 1NT with such a holding.

Answer 1

There are three big considerations if you are thinking of making a marginal penalty double.

1. Misfit

Penalty doubles work better if both sides are in a misfit, but especially the opponents. In this case we know that the opponents have at most seven spades between them, and the trump split is not 3-3.

There is no guarantee we have a good spot above 2S unless partner has a club fit.

2. Good trumps

K986 is a decent trump holding. With the spades on its right, it can likely expect two tricks (or else to score some ruffs). We are also likely to want to lead a trump to stop the dummy ruffing anything, and we have a decent lead in the 9.

3. balance of power

With 6 HCP to add to partner's 15-17, we have more than half the HCP in the deck.

All these suggest defending doubled. It is common for newer players not to double enough, but it is winning bridge to double with this hand (as long as you agree it is penalty! Many pairs do not...)

Also note that none of this depends on how strong 2S might or might not be, or how many spades it might hold. Trust your partner, not the opponents!

Answer 2

I ran a double dummy simulation with the excellent Deal 3.1 program by Thomas Andrews.

I'll attach more details about my assumptions and results at the end, but the answer to your main question is that it does make sense to double for penalty (if that is your agreement) in these circumstances.

In particular, the concern about doubling them into game is much smaller at matchpoints. This is not to say it is never relevant. However, in this case your partner is essentially choosing between two final contracts: defend 2 spades, or defend 2 spades doubled. At most other tables, your opponents are likely getting +90 or +120 in 1NT, and a few are probably facing the same problem as you. The 1NT players will beat you whether you double or not if opponents make two spades, so against them, doubling can never hurt and can only help. So your main worry is about other tables that saw an overcall. Here's where my simulation comes in: when playing double dummy, you beat 2S around 90% of the time. At matchpoints, you just need to squeeze past 50% to make that a winning move, so you'd prefer to defend 2SX over 2S.

There's a couple other questions hiding in here.

Is DONT a dangerous convention? Well, no, it's probably better than the standard defense against 1NT openings (i.e. all natural). It's based on a couple of insights. First, especially at matchpoints, if you rack up a lot of small gains from a convention, it's probably a winner even if the occasional loss is large. Second, opponents are really good at getting to good contracts when they can have an uncontested auction over 1NT. DONT allows you to disturb this auction when you have some distribution. It can cause opponents to get to suboptimal contracts, improves the defense if the opponents bid on, and it doesn't always go down when opponents defend. Sometimes it can go for a number or cause opponents to avoid a bad 3NT contract when missing important stoppers, but the idea is that it helps more often that it hurts. Larry Cohen writes more.

Would partner's double be for penalty? Maybe? That's definitely what SAYC says but I'm not sure it's what most people would assume by default these days. Should partner's double be for penalty? Maybe? Most people in US clubs that I run across that have any idea what their bids mean after opponents' interference play that doubles are negative, that is, takeout-oriented.

---

More on the simulation.

The script I ran accepts any deal in which

• south holds K986 QT T73 J642
• north is balanced (4333, 4432, or 5332 without a 5-card major) and has 15, 16, or 17 high card points (I ignored your adjustment for worthless doubletons).
• west has fewer than 12 hcp
• east has 6 spades or 5 spades and at least 4 cards in another suit and at least 12 hcp, and at least two face cards in spades

It then performs double-dummy analysis to determine the number of tricks east can make in spades and computes the score in 2SX. The results of analyzing 1000 random deals meeting the constraints:

--------------------------------------------------
| Value | Count |      Pct |  Cum Pct |   Pctile |
|-------|-------|----------|----------|----------|
|  -800 |    15 |    1.50% |    1.50% |  100.00% |
|  -500 |   162 |   16.20% |   17.70% |   98.50% |
|  -300 |   417 |   41.70% |   59.40% |   82.30% |
|  -100 |   322 |   32.20% |   91.60% |   40.60% |
|   470 |    72 |    7.20% |   98.80% |    8.40% |
|   570 |    12 |    1.20% |  100.00% |    1.20% |
|-------|-------|----------|----------|----------|
|       |  1000 |    0.00% |    0.00% |    0.00% |
--------------------------------------------------

The code for the computation:

source lib/score.tcl

south is "K986 QT T73 J642"

defvector facecards 1 1 1 1

shapecond spade_overcall_shape {
    $s >= 6
    || ($s == 5 && ($h >= 4 || $d >= 4 || $c >= 4))}

main {
    reject unless [balanced north]
    set hn [hcp north]
    reject unless {15 <= $hn && $hn <= 17}
    reject unless {
        [hcp west] < 12
        && [spade_overcall_shape east]
        && [hcp east] >= 12
        && [facecards east spades] >= 2}
    accept
}

set defend_hist [dict create]

proc write_deal {} {
    global score_hist
    set deftricks [deal::tricks east spades]
    dict incr score_hist [score {2 spades doubled} nonvul $deftricks]
}

proc flush_deal {} {
    # complicated histogram printing code omitted
}