The Great 'Thin the Field' Debate

There is a big debate about raising in limit hold'em. It is over whether you should tend to raise to "thin the field" (q.v. Sklansky) or not raise and "allow them in" (q.v. Caro). Thinning the field by raising tends to force players to fold who might have won a pot from you. So, this enables you to win more pots.

Here's a simplified example: Pocket aces win about four-fifths of heads-up confrontations. If you raise, thin the field, and get heads up against one player, you should win four times out of five. If you both invest $100, you should make $60 on this situation over time; ($100 × 2 × .80) – $100 invested = $60 profit.

There is another point of view in the "thin the field" debate. "Allowing them in" is based on the philosophy that if you have the mathematical edge, you want as many players as possible to contribute profit to you.

Here's a simplified example: Pocket aces win about three-tenths of the time against nine opponents. So, you'll lose seven times out of 10 but profit more over time; ($100 × 10 × .30) – $100 invested = $200 profit.

As a result, "allowing them in" often increases the size of the pots you do win, but reduces the frequency because it enables more people to draw out on you. In my opinion, both sides are valid, and they are not in direct opposition to each other. It all comes down to the specific situation.

In fact, I think the whole "thin the field" debate distracts from the most important issue – making money. In some situations, thinning the field makes more money than allowing people in, and in other hands the opposite is true. The focus must always be on creating profit for yourself and limiting it for your opponents.

Here's a basic example of pot odds: Let's say you're playing $20-$40 hold'em. You have the A K and are second to act against three opponents. The board on the turn shows 8 5 2 6 and the pot is $400 (10 big bets).

Well, you shouldn't really worry about what your opponents have, because seven cards give you the stone-cold nuts (the seven hearts that don't pair the board). Two more cards (the 5 and 6) give you a flush, a very strong hand. And six cards (the other aces and kings) give you a pretty good hand of top pair, top kicker.

Let's say the first player to act actually showed you that he already had two pair (6 5) and then bet. You still shouldn't worry. You should gleefully call for one big bet into a pot with 11 big bets. That's because seven out of 46 times, you will make the winning flush on the river. So, you're profiting by getting 11-to-1 on your money for a 1-in-6.5 chance of winning. You get to buy the river card cheap relative to the size of the pot.

That is the good and bad of limit hold'em; you quite often get to "buy low" to draw out on your opponents. Unfortunately, you normally can't "sell high" to prevent them from drawing out on you.

Now, let's look at the "thin the field" debate as it relates to the previous example. The board shows 8 5 2 6. The first player to act conveniently reveals his hand (6 5 for two pair), then bets $40 into the $400 pot. A poor understanding of "thin the field" would command you to raise to knock out the two players behind you.

But the best play would be for you to just call and "allow them in." That's because you can win only if a heart comes. Consequently, you want as big a pot as possible when you do win. There is no hand either person behind you can hold that can take the pot from you. If either has a set (and his river full house would beat your flush), you'd need a cannon to get him to fold. But that's irrelevant, because the 5 or 6 would give Mr. First-to-Act a full house that would beat your flush anyway.

Therefore, if you do raise Mr. First-to-Act on the turn, you just might get someone behind you with an overpair (10-10 or J-J) or a straight draw (10-7 or 10-9) to fold. But Mr. Overpair and Mr. Straight Draw can draw out on only Mr. First-to-Act. Neither player behind you can make a hand that would beat your otherwise winning flush. And raising them out loses the money you would have made if you make your flush.

Conclusion: You're an underdog to Mr. First-to-Act's two pair, so raising loses you profit to him. Raising can't knock out a player to earn you a pot you wouldn't have otherwise won. And, finally, knocking out players who don't take profit from you loses you their money when you win. This is a clear case of when raising to thin the field is incorrect.

Now, let's look at a mostly similar but crucially different scenario. In this example, let's say Mr. First-to-Act shows his Q Q and bets $40 into a $400 pot with the board of 8 5 2 6. You're still the underdog with the A K, but this time you have all 15 outs to beat him (nine hearts for a flush and six overcards for a bigger pair). So, now if you raise to thin the field, the two players behind you will face two big bets ($80) into a pot with 13 big bets ($520) in it. And they're probably worried that they might end up paying four big bets ($160) on the turn if there's a raising war.

Consequently, hands like the A 8, K 6, K 2, and even the 5 2 might fold to your raise. In this case, it is clear that thinning the field is a good option. That's because for the price of one extra bet, you could knock out players who would have won if your non-heart outs (the remaining aces and kings) come. So, that extra bet to thin the field earned 12-to-1 on your money for up to six outs (less than 7-to-1 against). Here, you would have correct pot odds to thin the field.

"Thinning the field" and "allowing them in" are important concepts to understand. If you're good at reading your opponents' hands and tells, you should appreciate that both concepts work in balance. Sklansky and Caro are pioneering poker geniuses. If you think they would have little agreement on the play of most limit hold'em hands, the odds are that you're the one who doesn't understand the situation.

More important than knowing most everything is knowing when you don't. I don't know everything. Tell me when I'm wrong.

Dan Abrams was the writer/producer of the documentary on the World Series of Poker in 2000 for the Discovery Channel, and the post producer/writer for the World Poker Tour in its first season. He is not Dan Abrams from MSNBC nor is he Daniel E. Abrams.