By: Jason Lake
So you're playing no-limit Hold'em for cash, with 100 big blind stacks, and it folds around to you in the small blind. You've got Six-Five offsuit. Are you going to play that hand? Probably. Now let's change the scenario: It's the final table at the World Series of Poker Main Event. You're one of three short stacks in the November Nine. It folds around to you in the small blind, and the big blind is the chip leader. How does Six-Five offsuit look to you now?
Not so good. If you open-shoved this hand, you would be committing what the kids like to call “ICM suicide.” With two other short stacks still in the tournament, it makes more sense to fold, and hope that one or both of them bust out before you do. Don't forget, there's a six-figure pay jump from ninth to eighth place. If you don't have a very strong hand in this situation – maybe pocket Nines or better – you should consider folding.
So what is ICM? It's a mathematical model that poker players use to figure out how much their chips are worth at any point in a tournament (before heads-up, that is). Once that value has been calculated, players can use some more math to get a sense of which hands to play and which hands to fold.
That's the short answer. To be more specific, ICM stands for Independent Chip Model. There are actually a number of different models used to calculate chip value this way; the two most popular of these are the Malmuth-Harville model and the Malmuth-Weitzman model. In 1987, Mason Malmuth broke ground on the ICM concept in Gambling Theory and Other Topics, then Bill Chen came along and fleshed these models out in The Mathematics of Poker (2006).
The models themselves are way too complicated to address here, but that's all right. For the most part, you'll never end up using ICM while you're at the table – unless you're working out a deal, in which case the action stops and everyone whips out their calculators. But it's a very important concept to understand. Once you wrap your head around it, you can start doing some calculations off-table as part of your poker homework. Software is available to help you get a sense of which hands are good to play, and which ones you should muck. Six-Five offsuit in the above scenario? Save it for the cash games.