the second coming of the second coming
Join Date: Jan 2005
Posts: 68,781
Yeah-- to elaborate a bit, let's use a simple example. A 10-person $10 sit-and-go that pays 50/30/20. At the start of the tournament, everyone's stack is worth $10. But if you win all the chips, you don't win $100, you win $50. So each chip is less valuable than the one before it. (One implication here is that having a short stack is still valuable as long as you're in the tournament.)
The major implication for ICM in tournament play is around bubbles and final tables. In these spots, $EV and cEV start to diverge significantly. So you generally want to avoid situations where you can bust out, usually by leveraging fold equity, adjusting your range to bigger cards to remove potential calling hands from other players, and/or avoiding playing pots against covering stacks whenever possible.
Let's say a final table of six looks like this:
70BB
40BB
25BB - you
15BB
10BB
8BB
and payouts are
1800
1200
800
500
300
200
Well, you have a third-place stack, and third-place money is four times as much as sixth. So if you get involved with a covering stack and bust sixth, that's a disaster for you.
Between the lost equity if you bust out, and the fact that (as described in the opening paragraph) each chip you win is less valuable than the chips before it, you gain much less real equity from doubling up than you lose from busting out. Therefore, you generally need a much bigger edge than in other stages of the tournament to put yourself at risk.
Sometimes that's as high as 70% equity (although I don't think it would be that high here, but I didn't want to run the numbers for a situation I just came up with off the top of my head).