So Expensive to be Careless


10 3
A J 10 3 2
A Q J 8 3
10
J 7 4 9
Q 6 5 4 K 9 7
9 5 4 10 7 6 2
Q 5 2 A J 8 7 6
A K Q 8 6 5 2
8
K Opening lead: various
K 9 4 3 Contract: 6 spades, 4 spades

Unlike some other hands, here the difference between 12 tricks and 13 was by and large, but not always, a matter of the opening lead. If you get a clubs or heart opening lead, you can't pick up 13 tricks. But if you don't get one of those two suits, then there's no reason not to take all 13. Running one's eye down the opening leads for those who made only 12 tricks, it's almost unanimously a heart or club. But there will pop up a spade lead or a diamond lead, and then 13 tricks should have been a piece of cake.
One declarer got a spade lead, continued drawing trump and then at trick four overtook the K of diamonds! For whatever reason, one cannot say. Another got a diamond opening lead and immediatelty cashed the A and went to draw trump. But why? That is, why the A of diamonds, not why drawing trump. If that's your next step, you can lead spades from either hand. So why not let the diamond lead ride.
I suppose counting, or lack of it is at issue here. But even if you haven't counted out the hand, why would you chew up a top card when you'll have an entry to the Ace later and are can lead trick 2's suit from either hand? No answer.
Anyway, lemme point out the matchpoint penalty both for those in slam and those in game: Six spades with an overtick got 86.59%. Six spades without an overtrick was worth 54.88%. That's a whopping 32 points lost for a pointless squandering of your K of diamonds when it should have been a winner in its own right. And at game level: three overtricks picked up 30%, two overtricks 12%. Not quite as big a disparity, of course, but 18 points for nothing (i.e., for the minority who didn't get a club or heart opening lead).
Oh, by the bye, 6 no (no overtrick) picked up 73.17%. So that 10-point advantage over 6 spades was worth an extra 19 points, while a 20-point advantage of an overtrick over 6 no was worth only 13% more. So you'd better pay attention to those overtricks in matchpoint scoring. In IMP scoring, you might as well pick up the easy overtricks (as here with a favorable lead) both for the small advantage and the respect of your partner. But you wouldn't want to take any risks to your contract for an overtrick there. And would you in matchpoints? I guess you might some time when you look at what you might gain.