Five-card majors for offensive purposes. However, if the trump cards break 4-1 or 1-4, then drawing trump will result in no trumps left for offensive purposes. The value of five-card majors can be understood then on two levels: But five-card majors have several drawbacks: Both partners must agree to follow the five-card major bidding treatment on their opening bid. Opener must have at least five cards in hearts or spades to start the bidding with that suit. Responder is expected to show support with three-card support, indicating an eight-card fit. With only four cards in a major suit, the opening bidder is
Jump bidding jumps from 0 to 8, the 10-bidder might quit and the 9-bidder will win and pay 8. Some authors claim that jump-bidding reduces the seller's revenue, since the signaling allows bidders to collude and reduce the final price. Therefore, it may be more profitable for the seller to use an auction format that does not allow jump-bidding, such as a Japanese auction. Other authors dispute this claim. Jump bidding In auction theory, jump bidding is the practice of increasing the current price in an English auction, substantially more than the minimal allowed amount. At first glance, jump bidding seems irrational.