What it is?
Favourable vulnerability means - you are not vulnerable and your opponents are vulnerable. Some people refer to this by the colour of the board "red vs white" or "red vs green" (when you look at your duplicate board, it has a colour to indicate the vulnerability).
Bidding decisions revolve around two main things
- The bonus for a vulnerable game is big. We want to make our Vul game bonus, and we want to try to make it difficult for our opponents to find their vulnerable game bonus.
- The penalty for going down not vulnerable is less. You can go 3 off doubled Not vulnerable and still will get a better score than the opponents making a vulnerable game!
There are some key ideas to consider when YOU are favourable, or when your opponents are favourable.
When you are favourable (you aren't vulnerable and the opponents ARE vulnerable)
This is often the time to be aggressive. More specifically
Light/Aggressive Preempts
Light/aggressive preempts or even preempting a level higher - bid a weak 2 with a 5 card suit and fewer points, for example at a recent world championship a player opened this hand favourable
The bid is made purely because of the vulnerability - the idea is to get in there, disrupt the opponents vulnerable game or even slam bonus. The basic idea - the opponents have a lot to lose, and you have less to lose since the penalty score is less not vulnerable.
State of the game: Players are preempting very aggressively when they are not favourable vulnerability. Always preempt, rarely/never pass instead of possibly preempting.
Light Overcalls
Light overcalls. The logic is very similar to preempts, you can overcall, partner can raise and you can get in the opponents way. For example
On this hand South overcalled with a very light hand - the idea - be aggressive and get in the way when not vulnerable, especially at your very first turn, especially on the one level! We hope to find a big trump fit, partner might raise you to the 4 level, making the opponents life difficult.
A lot of people worry and say "I have no points, I will get doubled and go a lot off". If you find a big trump fit, you will be fine, and if you go 2 or 3 off, it can often be for an excellent score.
Sacrifices
Sacrifices. This is the main time where sacrifices become possible, at all other vulnerabilities I recommend against sacrificing. Lets look at a spectacular example from a recent world championship.
Here south bid 4♠, with absolutely nothing other than a fit. When partner had 6 spades and they only went 2 off, they picked up a lot! (2 off is only 300, whereas the opponents were going to make +650 if they were left to play in 4♠). But even 3 off would've been a fine score!
When the opponents are favourable
When we are vulnerable and the opponents are NOT vulnerable, we can expect our opponents (if they have read this article!) to be aggressive. They will be preempting, overcalling and generally bidding aggressively. The antidote? Actually we have to be aggressive as well. Which is the opposite of what many people think. Most people think "I am vulnerable I have to be careful", however in fact you have to take risks, or else you will miss your vulnerable game bonus. Lets look at an example
This looks like a fairly minimum hand and many people would be "scared" to bid on the 3 level vulnerable. In actual fact we have to take risks, bid and potentially find our 4♠ game.
Common mistake: Being too conservative when vulnerable against Non vulnerable opponents. In actual fact we should typically get into the auction with a reasonable opening hand.