[CSGibson]

A lot of times on this forum I hear people justifying decisions they make by talking about offence to defence ratio (ODR). I have less understanding of what makes a good ODR. My vague thoughts are that:

The more shape the hand has, the more offensive in nature
honors in short suits are defensive-oriented

and that's it.

Another poster put a problem up where he was asking if he should preempt with

---

or something similar, and my first thought was that the hand had too much defense for a 4 spade call, but is this just a result of my poor understanding of ODR?

What other factors should I fine-tune in my assessment for ODR evaluations?

[TimG]

I think I first came across the term ODR in Partnership Bidding at Bridge by Robson and Segal. It is a book well worth owning.

[whereagles]

ODR = (nr. of expected tricks declaring) - (nr. of expected tricks defending)

Actually.. the word "ratio" would mean 'divided by', not subtracting one from the other. But I'm not sure how R/S meant it. In any case, I measure ODR with a minus, and then use

ODR of 5 = good for level 2 pree
ODR of 6 = good for level 3 pree
etc.

In the case at hand, we have:

Expected losers are 1/2 spade, 1 heart, 2 diams, 1 club, so 13-4,5 = 8,5 tricks on offense
Expected winners defending are roughly 1 spade, 1 club, 1 diam = 3.

ODR = 5,5 : which suggests a 1♠ bid, followed by 2 or 3♠ later.

Anyway, preemptive bids with a passed partner can be flexible because pard is broke and won't do much unless he has good fit, so it's ok to "preempt" with 4♠ on the given hand, provided you judge it's a good candidate to make.

[effervesce]

I second TimG's suggestion - however, the book is actually online for free (with permission from the authors).Partnership bidding at bridge (though it's still worth getting a hard copy imo). I highly recommend reading it; it has great stuff on partnership bidding, preemptive bidding and competitive bidding.

There are 4 aspects used when defining ODR:
a) your hcp strength
Now hcp is not the most important factor, but is still important in the ODR ratio. The ODR is defined by the offensiveness/defensiveness. A hand with no hcp can have no defensive strength at all, while in general both offense and defense increase with increasing hcp

Their example is this (given opps bidding spades):
8
9753
642
97653

and
8
A753
A42
QT653

the second hand here obviously has a smaller ODR ratio.

b ) shape
shortage in the opponent's suits are useful offensively, and the more distributional the higher the ODR

c) distribution of values
values in your and partner's suits are useful offensively, those in the opps defensively

d) type of values
in your suits, Qs and Js are offensive cards. In the opps suits they are defensive. Aces are neutral in that they can be useful both offensively and defensively.


Thus your example hand has a moderate ODR; it is good offense, but the aces contribute equally as well in defense.