kenberg, on 2017-September-16, 19:18, said:
But let us assume 2/1. Most everyone agrees that 1♠-2♥ shows five hearts. But after 1M-2m, choices have to be made.
I have played that bidding 1M-2♦ shows five diamonds. This is playable but then 1M-2♣ has to be a catchall. There is no choice. You can have the above hand after a 1♥ opening, and you could have a 3=4=4=2 shape after a 1♠ opening. You cannot rationally require that 1M-2m be based on five cards regardless of what m is.
I have also played, in fact I usually play, that 1M-2♦ can be on 4. This makes life easier, but sometimes you will wish it showed five.
I am not going to say which is best, I don't have a strong opinion on that. Even if you agree that 1M-2♦ can be on 4 you can still have an issue if you are 3=4=3=3 and partner opens 1♠.. You can cut down on the frequency by agreeing that 1♠-3NT shows a minimum hand, as game forces go, with exactly 3=4=3=3 distribution. I have never played that, but I can see the point.
Bidding agreements should be designed to differentiate hands so that the right contract can be reached.
This is done by using different bidding sequences.
Obviously the number of different hand types you can differentiate depends on the number of different sequences you have available.
In 2/1 game forcing the lowest contract after 2/1 is 3NT.
A little bidding theory can help here
The number of different sequences almost doubles with each additional step available.
So after 1M-2
♣ there are almost twice as many hand types you can show than when the bidding starts 1M-2
♦.
So why do we have problems differentiating club hands from balanced hands after 1M-2
♣ (Only 2 hand types)?
The answer is simple: Standard bidding violates what Rubens has called the "useful space principle (USP) ".
For example after 1M - 2
♣ bids being cheap should show frequent common hands and bids which use a lot of bidding space should be specific.
This maximizes the amount of information which can be exchanged. Relay system do this, but you need not play a relay system to accomplish this.
Standard bidding does not do this
For example after 1M-2
♣ the cheapest bid is 2
♦. But in standard this shows 4+ diamonds in openers hand. This requirement is quite specific and makes the bid rare, claiming that at least 50% of openers remaining cards are diamonds.
Nice when opener can rebid 2
♦, but making the situation bad when he does not have 4+ diamonds.
More likely opener has a 5M332 distribution, with which most rebid either 2M or 2NT, which is less specific but uses more bidding space.
Simply inverting these 2 bids, say the meaning of 2NT and 2
♦, after 1M-2
♣ game forcing makes your system more efficient and gives responder room to show what he got.
So agreeing that 1M-2
♦ showing 5+ diamonds and 1M-2
♣ being unspecific with regard to clubs is the way to go, but you have to invest a little bit in your continuations. Standard bidding is not very efficient here.
I have dwelt on this in a bit more detail in a recent Bridgeworld article where I have made suggestions how to improve standard bidding in a 2/1 context.
It is not so important whether you like my suggestions, what is important is to realize that standard continuations are not optimal.
Rainer Herrmann