Why might an auction go 1NT-3NT?

Question

Sort of a follow up question to this question.

In that question, the auction goes 1NT - pass - 3NT - all pass. The answers to the question point out that, by opening 1NT, declarer is saying they have ~16 HCP. Their partner, bidding 3NT in response to 1NT, indicates they have ~12 HCP.

Since there are 40 HCP total, partner should be aware that they together control ~28 of HCP. Since the first opponent has already passed, this suggests that the last opponent is likely to pass as well (even if the last opponent has all 12 of the remaining HCP, the odds should be that they can't make any contract above 1NT with only 12 HCP). Therefore, partner should be able to conclude that opponents will only be passing for the rest of the bidding, i.e., the rest of the bidding will be uncontested.

Given that, why doesn't partner raise by a smaller amount, taking advantage of the bidding room to communicate their hand more clearly with declarer? It seems like they have a lot of bidding room to do so, and opponents won't be interfering anyway. Phrased alternatively, if a bidding system suggests that you should respond to 1NT with 3NT if you're holding ~12 HCP, then it seems to be giving up percentage points because it's not making use of the forecasted bidding room.

I'm wondering why a bidding system might recommend making this bid anyway, or if there's some flaw in the above analysis.

Answer 1

I want to co-sign Tomek Czajka's answer and expand upon it a bit.

The reason the auction goes 1NT-3NT is that it maximizes your expected score. As a general rule, to make game in no trump with two balanced hands, you want a combined total of 25+ high card points (you can quibble one point in either direction). This isn't to say that you'll always make with 26 or always go down with 23. But: it is not efficient (or even really possible) to use bidding space to determine the exact composition of both hands to determine which suits are stopped, etc, and even if you did you're drawing a roadmap for the defense. Not all deals that go down double dummy go down in practice.

So: as responder after partner opens 1NT, if you are balanced (and don't think a major-suit game is worth exploring for), and you have values for game but not slam (so about 10-15 hcp), you should just bid 3NT. If you have a wide-open suit, the defense still has to find it with no real clues from the auction. It's also hard for them to know whether an active or passive defense is called for. As a defender against 1NT-3NT, holding KJxx xxx Qxx xxx, should I get active with a spade lead or stay passive with a heart or a club lead? It's impossible to say for sure, and if they guess wrong you collect the game bonus. And that's if they even have a right answer!

Answer 2

Other bids are reserved for other hands. For example, if you respond 2NT, you're indicating 8-9 HCP rather than 12 HCP. By bidding 3NT directly, you're giving information that you don't have those other hands.

You're not giving up very much by ending the exchange of information in this situation because with a combined 27-29 HCP and no 8-card combined major suit, you're unlikely to find a better contract than 3NT.

Using other bids to exchange information in this situation would have more downsides than upsides:

• it would prevent those other bids from being used in other situations when they are more useful
• you'd be giving more information to the opponents

Answer 3

The point count for the opening 1NT depends on the bidding system. In Standard American, it can be 15-17 or 16-18. In Acol, a weak no trump with 12-14 is common.

Assuming you're playing one of the above bidding systems, then the point count for the responding 3NT can be deduced by subtracting opener's point range from 25 high card points, which, as rude points out, is what you need on average to make game.

Why would you bid directly, rather than showing more of your hand? There are two major reasons, both involving the opponents. The first is to avoid divulging information. If you embark on an extended bidding sequence, arriving at 3NT having shown short diamonds, the opposition has an excellent view of where to attack. The direct sequence denies them this.

Secondly, if, over 1NT, you decide to show a suit, you make it easier for the opponents to come in. Once they have shown a suit, again, the opening lead is much easier. As explained above, the opponents may have up to 15 HCP, and if they have an unbalanced hand, two or three of their suit may be perfectly playable or an excellent sacrifice against your game.

One final point, which you did not address directly, but may be relevant for you: in competition bridge (pairs or teams), you bid games with a 40%-50% chance of making (depending on vulnerability). So you want to bid thin games, and if you can deny the opponents information, you will make more of them.

Answer 4

Because neither player is interested in anything else

Given that, why doesn't partner raise by a smaller amount, taking advantage of the bidding room to communicate their hand more clearly with declarer?

In most systems, 1NT is a relatively specific opening bid that gives much more information than a typical suit opening. Typically it indicates both a narrow HCP range and a balanced hand. If partner's hand is also balanced, it's between unlikely and impossible that a massive suit fit is being overlooked. On the rare occasions that, say, both players have a doubleton in the same suit, at least one of them can be expected to hold the A or K, so skillful play has a high probability of avoiding 5 losers. Overall, 3NT is likely to be made, and there is no reason to suspect 4H or 4S would be any easier.

Since 3NT is a game contract, there is no benefit to ending up at the 4 or 5 level. At contract it only moves a few points below the line, but you still would have made game anyway, and don't get any extra credit towards another game or towards the rubber. Similar logic applies to duplicate scoring.

Since excellent suit fits and shortages (i.e. ruffing potential) are both so unlikely, the only realistic route to slam at this point is through sheer high-card strength. But if you know that opener has no more than (typically) 18 HCP, it's easy to conclude that the strength needed for slam just isn't there.

Therefore, trying any other bids is at best a waste of time; at worst, it leaks information that could help the defenders select an opening lead or infer a weak or unstopped suit.

Answer 5

A bit late to the party, but since I wrote in answer to that question:

This auction ended at 3NT (why, I won't go into, but there's a bonus for making it that you don't get with any lower bid).

You're now asking a question that needs the answer to "why". Now, all the answers given are accurate and good - for someone who plays bridge. But since I know you don't, here's the information that answers "why".

This will be a story in sections and footnotes(0). Footnotes aren't necessary to understand...

Bridge deals are scored (provided declarer makes the contract) like this:

Trick score ("odd tricks" are defined as "tricks more than 6 of the 13"):

• 20/odd trick with clubs or diamonds trump
• 30/odd trick with hearts or spades trump
• 40 for the first odd trick, 30/further at notrump

Which isn't much. But there are big bonuses for bidding and making contracts at certain levels(1):

• 2000 for grand slam (7 level, make all the tricks)
• 1250 for small slam (6 level, all the tricks but one)
• 500 for game (100+ trick score)(2)
• 50 for partscore (<100 trick score).

Emphasis on bidding. If you take 10 tricks in spades, you get 120 trick score, but if you don't contract for at least 10 tricks (bid 4 or 5 Spades)(3), you only get the partscore bonus.

So, what are the "game" contracts? 100/20 is 5 Clubs or 5 Diamonds; 120/30 is 4 Spades or 4 Hearts; (100-40)/30 is 3 Notrump.

Now, remember that the goal of the (uncontested) auction is to answer the questions "where" and "how high". Once a player knows the answer to both of those questions, they set the contract and partner passes(4).

But since you get the same "trick score plus game bonus" for 3NT, 4NT and 5NT, there's no reason to want to play those last two(5). So, unless 6NT or 7NT is in the picture, if "where" is notrump, and you have the strength for game, "how high" is 3.

With that knowledge, read the other answers. As an example:

1NT is a very well-defined bid - no long suit, no short suit, and usually a 3 HCP range (15-17 is common). So when partner bids that, it is easy to see that with responder's hand:

• we have enough for game;
• we don't have enough for slam; and
• we don't have an 8-card major fit.

If that's the case, responder knows "where"(6) - notrump - and "how high" - 3NT. So they bid it, and partner passes.

Similarly, if responder knows that "we don't have enough for game" and "we don't have a good fit", they just pass 1NT.

If responder isn't sure, then other bids between 1NT and 3NT come out:

• if responder has a 4-card major and wants to know if opener has 4 to match, they can bid 2♣ systemically asking partner to bid one if they have one(7).
• if responder has enough for game if opener is at the top of their range, they can bid 2NT, which partner will pass with a minimum or bid 3 with more.
• if responder wants to play a partscore or game in their long suit, they have bids that allow that.
• ...

But "you bid 3NT over 1NT" when you know that's where you want to play. It's very common.

0: GNU Douglas Adams.

1: Yes, I know, NV bonuses are different, and I've combined "game+slam bonus" for simplicity. This is Wrong, but not incorrect.

2: okay, at duplicate. Rubber bridge is fascinating, but again, "simplicity".

3: This is the difference between Contract Bridge (what everybody plays today) and its predecessor, Auction Bridge (where you got the bonuses for game or slam whether you contracted for them or not). Contract and Vulnerability (1) are what made the game what it is today.

4: Handwaving like mad here. Please let me? We're talking a 1NT "responder is captain" auction.

5: In fact, that's why 4NT is almost always reserved for asking for Aces, and 5NT for some other conventional ask (except over 1NT openers, yes, I know. Again, simplicity). Nobody wants to play 4NT or 5NT when they could have played 3NT.

6: Rule of thumb is that you can take one more trick in an 8-card fit than at notrump. So 4 hearts is better than 3NT with a heart fit. But it is almost always easier to make 3NT than 5 of a minor.

7: which is why I said later in my response to the previous question:

There's little to go on with 1NT-3NT, but there is a strong implication that a major suit (hearts or spades) will work better than a minor suit (clubs or diamonds). Because of the way the scoring system works, finding a major suit fit is a big thing, and LHO hasn't even looked for one - so they don't have one.

Answer 6

There are many, many ways to bid your hand after your partner opens 1NT. If you bid 3NT immediately, it shows (in most cases) a hand with no 4-card or 5-card major, that is strong enough for game but not strong enough for slam. So 3NT is very probably the best contract to play in.

With a 4-card major, you can bid 2 Clubs, the Stayman convention, that asks partner to bid their 4-card major if they have one. That way, you can reach four of a major if you have eight trumps between you.

With a 5-card major, you can make what is known as a transfer bid (if you have agreed this with your partner before the game). This shows five cards in the next suit up (so e.g. 2 Diamonds shows 5 Hearts); after partner bids 2 Hearts, you can make a further bid (2NT or 3NT with only five Hearts; 3 Hearts or 4 Hearts with six or more Hearts). So holding three or more Hearts, your partner will correct your NT bid to a Heart contract.

And so on.