Advanced Scoring
Vulnerability
The scoring basics page skipped a couple of details about undertricks and slam bonuses. But to explain them, we first have to understand what it means to be vulnerable
A partnership is vulnerable if they have won 1 of the 2 games necessary to complete the rubber. At the start of the rubber, no one is vulnerable. Once a partnership is vulnerable, they are vulnerable until the rubber is over. The rubber ends when a vulnerable partnership wins a game.
If a vulnerable partnership fails to make their contract, the other side gets 100 points per undertrick instead of 50.
Also, if a vulnerable partnership makes a small slam, they get 750 points instead of 500. If they make a grand slam, they get 1500 points instead of 1000.
The increased penalties for undertricks discourage a team that has won 1 game from sacrificing (bidding a contract they know they will lose) to stop the other team from winning a game.
Doubles and Redoubles
The auction page mentioned double and redouble. It said they change the scoring, but not the number of tricks or the trump suit. Here we’ll see how they effect the scoring.
Trick Score
The first thing that doubling does is to double the trick score. Redoubling makes the trick score 4 times as large. 2♥ doubled has a trick score of 120 = 60 × 2. 1NT doubled has a trick score of 80 = 40 × 2. 2♣ redoubled has a trick score of 160 = 40 × 4.
Insult Bonus
The next thing doubling does is award a bonus if you make your bid. This is called the Insult Bonus. The idea is that by doubling, you implied that declarer couldn’t make the contract. The insult bonus is 50 points for a doubled contract or 100 points for a redoubled contract. This goes in the bonus column.
Doubles and Vulnerability
Doubling also changes the value of undertricks and overtricks. The values for doubled undertricks, like regular undertricks are affected by vulnerability. Doubled overtricks are also affected by vulnerability. Only the vulnerability of the declaring side affects scoring.
Doubled Undertricks
The first doubled undertrick is always twice the value it would be undoubled. It is 4× if redoubled. So 1 doubled undertrick for a non-vulnerable declarer gives the opponents 100 points. 1 doubled undertrick for a vulnerable declarer gives the opponents 200 points. Later undertricks cost even more.
For a vulnerable declarer, the 2nd and later undertricks are 300 points. This means that 1, 2, 3, 4, 5, … undertricks award the opponents 200, 500, 800, 1100, 1400, … points.
For a non-vulnerable declarer, the 2nd and 3rd undertricks are 200 points. The 4th and all later undertricks are 300 points. The same 1, 2, 3, 4, 5, … undertricks award the opponents 100, 300, 500, 800, 1100, … points. Note that from 500 onward, the values are the same, and that non-vulnerable reaches 500 one trick later than vulnerable.
Redoubled undertricks are exactly twice the value of doubled undertricks for all vulnerabilities and any number of undertricks.
Doubled Overtricks
For a non-vulnerable declrarer, each doubled overtrick is 100 points. For a vulnerable declarer, each doubled overtrick is 200 points. Redoubled overtricks are twice the value of a doubled overtrick.
Slam Bonuses
Slam bonuses are affected by vulnerability, but are not affected by doubling, nor by re-doubling. The bonus for a vulnerable small slam is 750 points instead of 500. The bonus for a vulnerable grand slam is 1500 points instead of 1000.