Research
A study of 3,075 deals that kept the strong jump shift at 19 or more points and, playing 2/1 Game Force, limited it to suits whose ordinary response would have been at the one level.
A jump shift is a response in a new suit one level higher than necessary, for example 1♦ – 2♠. Our sources agree it is a strong bid in an uncontested auction, but not on the details. One asks for 19 or more points. Another accepts about 16 and a good suit, and treats a jump to three of a lower suit as invitational. A third says only that the jump shift is strong. A second question was whether a jump shift helps at all when the partnership plays 2/1 Game Force, where an ordinary two-level response already forces to game.
The study used every stored deal with an uncontested one-of-a-suit opening in which an unpassed responder held 16 or more points counting length and a side suit of five cards or more: 3,075 deals. BidMaestro bid each deal from the opening onwards under each candidate rule, with all four players using the same system.
Nine rules were tested. Eight were a jump shift on 16, 17, 18 or 19 points, each in two forms (any strong hand, or only a hand with one long suit), with the jump made over every opening. The ninth had no jump shift at all. They were compared with the rule the app played at the time: 19 points, over minor-suit openings only.
The nine rules were measured on 2 September 2026. The comparisons of 1♥ with 1♠ and of the minor-suit jump below were measured on 4 September, after other improvements to the app’s bidding, so the two sets of figures cannot be compared directly.
Each final contract was scored on the cards as dealt, played with all four hands visible (Double Dummy), from the point of view of the side that opened. Because one layout of the cards can favour or penalise a rule by chance, 2,305 of the 3,075 deals were also re-dealt 200 times. The opening side’s cards were kept and the opponents’ reshuffled, and the contract was scored against the average of those layouts. The other 770 deals were scored on the dealt cards only. To be adopted, a rule had to score better on both measures by more than its margin of error.
Over 1♣ the strong jump shift is used in any suit; over 1♦, hearts or spades; over 1♥, spades only; over 1♠, none. Where the ordinary response is already a two-level game force, the jump uses a level and gains nothing. With 2/1 Game Force switched off, the jump shift is used in every suit, because a two-level response then forces for one round only. The 19 points count length, and the suit must be a good one of five cards or more.
Compared as a whole with the rule the app played before, the new rule gained about 170 points per changed deal over 85 deals (59 better, 16 worse), reaching 23 more slams and missing 2. The bid itself is described on the jump shifts page.
The study measures the jump shift together with BidMaestro’s own later bidding; a partnership with different continuations could reach a different result. 3,075 deals is a small sample.
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