How to Determine Which Cards are Good for Players in Blackjack
We know that keeping track of cards already played tells us about hands yet to come. But to make use of this information, we need to know which cards are beneficial to us as players, and which cards are not. Once we know this, tracking the cards played will tell us when the remaining deck is to our liking. Ultimately, we will bet small when the remaining deck is unsavory, and bet big when it's juicy.
To help determine which cards are good for us and which are bad, we must consider the rules of the game and the difference
in playing strategies between a basic strategy player and a dealer employing the house rules. A lot can be gleaned from this comparison; there are several factors at work that show why it's important to be able to distinguish between decks made up of predominantly high cards and decks made up of predominantly low cards:
1. The payoff structure for naturals favors the player.
When the remaining deck has an excess of aces and tens, you're more likely to be dealt a natural. This fact favors the player. Although the dealer is always as likely as we are to receive a blackjack, our two-card 21 is paid at a premium. Imagine a game in which there is at least one natural guaranteed to show each hand; that is, on each deal the player and/or dealer will have a blackjack. Let's suppose we are betting $20 a hand. When we and the dealer get a blackjack, we push and no money changes hands. When the dealer has a natural and we don't, we lose $20. But when we have a natural and the dealer doesn't, we win $30 because our blackjack pays 3 to 2. We come out far ahead overall.
2. The dealer must hit until reaching a pat total of 17 through 21.
All casino dealers play by a fixed set of rules: any hand of 16 or less must be hit and, of course, any hand of 22 or more is busted. Totals of 17, 18, 19, 20, and 21 can be thought of as a "safe zone" into which the dealer climbs, then stops. Clearly, with an excess of high cards remaining, the dealer's chances ofreaching the safe zone, without going beyond it, when drawing to a stiff total decrease. On the other hand, if a lot of small cards remain, the dealer is more likely to draw to a pat hand. When an excess of big cards remains, the knowledgeable player can choose to stand on a stiff hand, forcing the dealer to draw from a deck rich with high cards and (hopefully) bust.
3. When doubling down, the player is usually hoping to get a high card.
Two conditions must generally exist for us to double down: (a) we expect to win the hand; (b) we are satisfied drawing only one more card. Furthermore most double downs occur against a weak dealer upcard (a 3,4,5, or 6). An abundance of high-valued cards helps us in two ways here. Our hand is likely to improve greatly (if doubling on a total of 10 or 11), and the dealer is more likely to bust, especially when showing a weak upcard.
4. Many splitting opportunities are more favorable with an abundance of big cards left in the deck.
A preponderance of high cards is usually beneficial to us when splitting, regardless of whether we are splitting offensively or defensively. This is especially true of splitting 7s, 8s, 9s, and aces.
5. Insurance can become a profitable bet.
This should not be underestimated, as the proper use of the insurance wager while card counting is worth roughly 0.15% (or more). We should never take insurance with no knowledge of deck composition. But if we're tracking the game and know that the ratio of tens to non-tens is large (greater than 1/2), then insurance should be taken. The great thing about insurance is that you take it only when you want to - it's an optional side bet that can be put to good use by a card counter.
These are the main reasons why certain card denominations are favorable or unfavorable for the player. Clearly, a deck relatively rich in high cards (or, equivalently, poor in low cards) is good for the player. Conversely, a deck rich in low cards (poor in high cards) favors the dealer.