IMPACT of vulnerability is much misunderstood. I often hear rubber bridge (or Chicago or teams for that matter) players bid a marginal game with the shrug of ‘Ah, well, we’re only non-vulnerable’. Wrong! The value of the vulnerable game is much more than the non-vulnerable game: you should stretch more when vulnerable.
How about at pairs? The first thing to say is that when the auction is uncontested, vulnerability is irrelevant. It doesn’t matter one jot whether you are scoring 620 or 420 versus 170, because it is not the amount of difference that matters.
Say for example that every table sees North-South declare no-trumps. It does not matter whether the bonus for game is 300, 500, or one million! It’s all relative, not absolute. If all other North-Souths are making 1NT +1, you will get the same top for making 1NT +2 as you will for making 3NT exactly. Conclusion: don’t push for close games.
Might South be able to make 4 after hearing partner make a single raise? Sure. But will he make a game try?
No, he won’t. It is relatively unlikely that game will be on; further, if South plays the hand in an inspired fashion and makes ten tricks, he will surely get a good matchpoint score for +170; he does not need the game bonus (unlike at teams and rubber, where he would like that bonus).
Let’s look at the play in 2. Declarer wins the queen of hearts lead with his ace (duck, and West might find an unwelcome switch to a trump). At trick two he makes the key play of leading towards the jack of diamonds. Note that leading towards the diamond king can come next, should the jack of diamonds lose to the queen.
Here West rises with the queen of diamonds, meaning that now the diamond jack has a material value. West cashes the jack and ten of hearts, then switches to the seven of spades. Winning with the spade king, declarer leads the diamond jack. West wins with the ace of diamonds and leads the eight of spades. Declarer wins with the spade queen, then ruffs the eight of diamonds with dummy’s last trump. Ace of clubs, club ruff, then the ace of spades drawing West’s spade ten bring his trick tally to nine: +140 and a good match-point result.