Natural Bidding in Bridge:
The Sevenfold Way
Johannes Koelman
In the game of bridge, a natural bidding system denotes a collection of bidding agreements based on the principle that (with very few exceptions) each bid can be seen as a proposal for a contract. In particular, in natural bidding systems an opening bid at the lowest level guarentees a minimum length of the suit bid, and is non-forcing. Typical for natural systems is that the sum of the minimum lengths of the four suits that can be bid at the lowest level adds up to 16. The simplest example of this 'rule-of-16' being four-card major systems in which each bid in a suit at the one-level guarantees at least a 4-card in the suit bid.
As a consequence of this 'rule-of-16', natural bidding systems are often codified into a numerical code consisting of four non-increasing digits that add up to 16 (see: http://gerbenbridge.blogspot.com/2005/12/4-and-5-card-majors.html). For example, the code '4444' denotes systems in wich each of the four suits opened guarentees a 4-card or longer. Similarly, the Standard American (5-card major & best of both minors) system can be labelled '5533'. In total we can distinghuish five groups of natural systems: 4444, 5443, 5533, 5542 and 5551.
Yet, a more descriptive coding of natural bidding systems can be derived by noting that in natural bidding systems the sum of the lengths of the four suits would add up to 17, were it not that in each case one particular distribution prevents the sum of 17 to be reached. For instance, would the distribution 4=3=3=3 (4 spades and 3 of each other suit) not occur, one could agree to open spades on a 5-card or longer and the three lower suits on a four card or longer. Such a '5444' system requires one to agree how to handle the 4=3=3=3 exception. Two possible agreements are 1) to open this particular distribution in spades, or 2) to open these hands in clubs. We will codify these two possibilities as (5)444 and 544(4), respectively. Note that in both cases the digit between brackets denotes a suit length that is guarenteed except for one particular distribution for which the suit length is one shorter than indicated.
Using the notation based on the 'rule-of-almost-17', we can distinghuish seven subgroups of natural systems: (5)444, 544(4), 5(5)43, 55(4)3, 554(3), 55(5)2 and 555(2). Each of these will be discussed in more detail below.
(5)444
Each suit opened guarentees a fourcard or longer, whilst spades is opened on a fivecard unless the hand has a 4=3=3=3 distribution. The prototypical example of this thoroughly natural system is the original Acol system with its fourcard majors.
544(4)
A variant of the Acol system popular the Netherlands since the end of 80's. The 1C opening denotes a fourcard or longer unless opener holds a 4=3=3=3 distribution. The Dutch pair Leufkens-Westra won the 1993 Bermuda Bowl utilising a natural system based on this structure.
5(5)43
Other variants of the Acol system - such as Swiss Acol - comply with this structure. The 1S opening guarentees a fivecard, but the same is not true for a 1H opening. Following this opening, a fivecard hearts can be inferred only from later bidding (e.g. when a 1S response to a 1H opening does not get raised).
55(4)3
Systems like SAYC comply with this fivecard major structure. Both the 1S and the 1H opening denote fivecards. In the absence of a fivecard major the longest of both minors is opened. The 1D opening denotes a fourcard or longer unless opener holds a 4=4=3=2 (4-card in both majors and a doubleton clubs) distribution.
554(3)
Following Polish-club type systems, under this structure the fivecard majors is combined with a fourcard diamond opening by moving all the opening length ambiguity to the club suit (which can be opened on a doubleton in case of a 4=4=3=2 distribution). Italian 2/1 sytsems follow this 'doubleton club' structure.
55(5)2
Not only the major openings, but also the diamond opening denotes a fivecard unless opener holds a 4=4=4=1 (singleton club) distribution. Notice that all truly balanced hands (4-3-3-3 and 4-4-3-2 patterns) are opened 1C. As a consequence, the 1D, 1H and 1S openings all guarentee some 'shape', a feature useful for partner in cases when a competitive bidding develops. The Dutch system 'Boring Club' utilises this structure.
555(2)
Under this structure utilised in 'Phoney Club' systems, any suit opened denotes at least a fivecard, except for the club suit which can be opened on a singleton in case of a 4=4=4=1 distribution. Even when the 1C opening is non-forcing, purists might argue whether such a system should be classified as natural!
Whilst each of the above systems has its advantages and disadvantages, it is clear that the general concensus leans towards eliminating ambiguity on the minimum length of the major suits at the expense of increasing the ambiguity of the minor suits. As a result methods like 55(4)3 and 554(3) currently flourish. It is interesting to note that - especially in Europe - an evolution towards 'short club methods' (554(3) and 55(5)2) is apparent. These methods often pair a highly increased frequency of 1C openings to conventional responses such as transfer responses.
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