In a recent talk to the Ocala Duplicate Bridge Club, Jon Shuster of Gainesville presented a selected analysis of 717,102 computer generated bridge hands. One part of his inquiry involved the usefulness and frequency of occurrence of the preemptive jump raise when using the Inverted Minor (“IM”) convention.
For the IM analysis he limited his inquiry to only the preemptive raise to be made with less than 10 hcps, and broke that down into a minimum raise of 1-6 hcps and a good raise of 7-9 hcps. Some criteria need to be mentioned to fully appreciate the IM analysis:
(a) With the minimum preemptive jump raise (1-6), Jon permitted the preemptive raise to be made holding a 4 card major.
(b) With the minimum preemptive jump (1-6) raise he stipulated 5 card support in both clubs and diamonds, but with the good preemptive jump raise(7-9), he permitted the raise to be made with 5 clubs or 4 diamonds (but not on 4333 hands).
(c) Most importantly he imposed a minor suit opening protocol of always opening 1 diamond unless the hand held 2 diamonds and 3 clubs (4423).
It is not necessary that you agree with Jon’s assumptions. Without assumptions analysis cannot be made. Other assumptions may vary the conclusions.
In one part of this analysis he tested the effect of permitting the good preemptive jump raise (6-9) FROM 1 club to 3 clubs with only 4 card club support to determine how this affected the frequency of finding opener with a 3 card suit. His results showed that the frequency of finding opener with a 3 card suit when raising to 3 clubs with only a 4 card club support is anywhere from 2-3 times more likely (depending on the seat in which opener opened). Central to this conclusion is Jon’s assumed protocol in the opening of minor suits.
If you changed the assumption to open “better minor”, I am confident that the relative difference of three card suits would be smaller between clubs and diamonds since you always open the better of the two suits. That is not a pitch for “better minor” nor is it a recommendation that you make a good inverted raise with 4 clubs. Assuming you apply Jon’s criteria, he found that when you make a good IM jump raise with 4 card diamond support, you expect to find opener with a 3 card diamond suit only about 8% of the time. It is easy to see that your support protocol has to be tied into your minor suit opening protocol to make a comfortable decision about the level of diamond support required for a preemptive jump raise.
The more important revelation from Jon’s study of IM preemptive raises deals with their frequency of occurrence. Let’s assume you play duplicate bridge twice a week or 104 times a year. If you use only minimum preemptive minor suit raises (1-6), you will see one about every 4 months. If you use only good preemptive minor suit raises (7-9), you will see one about 11 times a year or once every 9.5 sessions. If you use both minimum and good preemptive minor jump raises, you will see them 15.5 times a year, once every 6.7 sessions.
What are the practical aspects of this. Unless you play several times a week, you have to question whether using inverted minors is worth the effort. Every convention takes up "gray matter," so if you have reached your “Peter Principle”, this might be a good one to consider eliminating. Conventional bids also raise the possibility of missing an alert or missing the bid entirely, which could lead to disaster,
Finally, there is much more to the inverted minor suit raise convention that just the first response. If you are not familiar with the recommended continuations, you very likely will end up with a poor result. My view of this was substantiated by a comment made by Frank Stewart in his bridge column on March 25, 2007. After a discussion of an inverted minor hand, Stewart concluded:
“I don’t care for inverted minors, not because I think the idea itself is theoretically unsound but because the development of the auction will be confused unless a pair spends considerable time in discussion.”
I’ll give you a clue, I think the only correct places to pay these hands is either 3 of a minor or 3 no trump since you don’t have 8 major suit cards. Even with a single raise (10+) you can bet that either 3 of the minor or 3NT will be a top board, but unless you find opener with stoppers in both majors, getting it right can be an elusive proposition.
On the other hand, with long minor suit support and less than 9 points, a part score in no trump is often the best contract. It will be easier to find that contract if you do not take up your own bidding space with IM. The better advice is to simplify your convention card and leave those problems to someone who needs them.