What is Duplicate Bridge?

Duplicate bridge is a variation of contract bridge played at our Club. It is called duplicate because the same bridge hands are played at each table and scoring is based on relative performance. In this way, every hand, whether strong or weak, is played in competition with others playing the same cards, and the element of skill is emphasized while the element of luck is deemphasized. Duplicate bridge is in contrast with rubber bridge, where each hand is freshly dealt and where scores may be more affected by chance in the short run.

In duplicate bridge, a player plays with the same partner throughout an event. The two are known as a "pair."

Hand carriers, or "boards"
Hand carriers, or "boards"
Bridge boards, simple four-hand card holders, are used to pass the hands intact to the next table that is to play those cards.

Final scores are calculated by comparing each pair's result with others who played the same hands. Furthermore, games are "stratified," meaning a pair's performance is measured against other pairs with similar levels of experience.  In addition, we frequently hold Novice and Beginner games, where highly experienced pairs are not allowed to play.

Bidding boxes are used to facilitate the mechanics of bidding and minimize the noise level.  There is an article about Bidding Boxes here.

A bidding Box, 4 are used at each table
A bidding Box, 4 are used at each table

Each game is overseen by a Game Director, a sort of referee who seats the pairs, and directs which hands are played when.  The Game Director also enforces the rules, which are a little different than rubber bridge.  The rules have been established by the national organization, the American Contract Bridge League, or ACBL.

Club Games

A scoring unit
A scoring unit
In club games, each deal is played some number of times by different players, after which all the scores are compared. Immediately after a hand is played, the North player records the Contract and the result in a hand-held device the size of a calculator, and allows the East player to acknowledge its correctness. It transmits the result wirelessly to the director's computer. This allows results to be posted at the club and on The Daily Recap very quickly after the end of play.  There is an article about using the unit here.

The usual form of overall scoring is Matchpoint scoring. Every pair plays against a number of opposing pairs in successive rounds, depending on the size of the field. Games with up to about a dozen tables are usually played either as a Mitchell movement (each North/South pair plays against all or most East/West pairs) or a Howell movement (each pair plays against all or most other pairs, and switches between North/South and East/West as required). A Howell movement is typically used if there are fewer than about 7 tables. With larger fields the game can be split into separate sections (every section operates its own separate movement, but the scores are compared across all sections); each section normally plays a Mitchell movement.

The game consists of a number of rounds, which each round playing a number of boards, usually two to five, against the same opponents. After each round, some or all of the players move along to another table, according to a prescribed movement, so that each pair plays against a different pair in each round; the boards are also moved in an opposite direction. The movements are set up so that no pair plays more than one round against the same opponents, and, of course, no pair plays the same board more than once. The Game Director will select the movement depending on the number of pairs playing, to allow them to play the desired number of boards each, without repetition. A session typically consists of between 24 and 28 boards in total, but this can vary.

Typically, 7 or 7½ minutes are allowed per board, with hospitality breaks every hour or so.  A typical session will thus last about 3¾ hours. If there is an odd number of pairs, one pair will have to sit out in each round.

Pair "movements"

The Mitchell movement is the most common. The North-South pairs remain stationary. After each round, the East-West pairs move to the next higher table and the boards move to the next lower table. If the number of tables is odd, every E-W pair will play different boards against every N-S pair after the full circle. In case of an even number of tables, the East-West pairs are told to skip a table after about half the rounds so that they do not encounter boards that they have already played; alternatively ("Relay-bystand Mitchell"), a "bystand" (playerless table) is introduced, while the two tables farthest from the bystand share the boards from each round (the "relay"). Usually, the bystand is placed halfway through the field (e.g. between Tables 5 and 6 if there are 10 tables) and the relay between Table 1 and the last table. The "perfect" Mitchell is seven, nine, or thirteen tables, with four, three, or two boards per round respectively: all players play all boards, and all pairs of each direction play against all pairs of the other direction.

Sample Howell Guide Card
Sample Howell Guide Card
The Howell movement is sometimes used instead, when there is a relatively small number of tables. This movement is more complicated and varies according to the total number of pairs. All boards and most pairs move after every round according to guide cards placed on the tables. The Howell is sometimes considered a fairer test than the Mitchell, because each pair faces all or nearly all of the other pairs, not just the pairs sitting in the opposite direction. However the fairness of a movement depends not only on who one plays against but also to a considerable extent on one's indirect opponents, i.e. those who play the same cards as you do. The Howell also tends to be more error-prone than the Mitchell due to its greater complexity. Ideally the number of rounds will be one less than the number of pairs competing, so that each pair plays one round against ever other pair. Each round will usually consist of either 2, 3, or 4 boards. However sometimes this produces an inconvenient total number of boards to be played. To avoid this, a "reduced Howell" or "three-quarter Howell" movement is often played, with fewer rounds and usually with more than one stationary pair, so that the number of rounds plus the number of stationary pairs equals the total number of pairs.

Whatever movement is used, if the number of pairs is odd, obviously one pair must sit idle during each round; that situation is referred to as a sit out. In that undesirable case, the missing pair (sometimes called the phantom pair) is treated as if it exists, i.e. the movement is set up for one more pair, requiring half that number of tables. The phantom pair may be North-South, East-West or an arbitrary pair number in a Howell movement.

Compared to rubber bridge

Scores of a Duplicate Game
Scores of a Duplicate Game
Duplicate bridge, especially matchpoint games, differs significantly from rubber bridge.  While the goal in rubber bridge is to win more points than the pair of people you are playing against, in duplicate bridge the goal is to do better than other pairs playing exactly the same cards. Because of this, strategies are different. In rubber, 30 points above the line for an overtrick is unimportant and hardly worth risking a set. In match-points duplicate, it is common for those 30 points to mean you get a top score instead of average – and may be worth risking going down. In rubber, an occasional 800-point penalty is disastrous, but in matchpoints it is no worse than any other bottom score.

A more subtle difference is in the bidding of partscore hands. In duplicate bridge, once a pair recognizes that they are playing for part score (less than a game), their objective is to win the auction with the minimum bid. In rubber bridge, it may occasionally be desirable to bid above this minimum as points below the line may be needed to complete a game.

Duplicate bridge also has the distinction of compensating for a bad run of luck with the cards. A pair that has had poor hands all night may still have the highest score for the evening – as long as they play those cards better than the other pairs with the same poor cards (however in such cases the pair will probably have had less opportunity to exercise skill and their result will be more heavily dependent on the skill displayed by their opponents).


See also: Are you new to Duplicate Bridge?

See also: ACBL's Introduction to Duplicate

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