Card counting is a mathematical strategy used primarily in blackjack to track the composition of cards remaining in the shoe. The fundamental principle is simple: different cards have varying impacts on the player's probability of winning. When high-value cards (10s and Aces) are depleted from the deck, the dealer's bust probability decreases while the player's blackjack frequency increases. Conversely, when low cards (2-6) are removed, the composition shifts in the casino's favor.
The strategy emerged in the 1960s when mathematician Edward Thorp published "Beat the Dealer," which demonstrated that card counting could theoretically reduce the house edge in blackjack. His work was groundbreaking because it proved that casino games, previously thought to be purely games of chance, could be influenced through mathematical analysis and disciplined gameplay.
The basic principle involves assigning point values to cards: typically +1 for low cards (2-6), 0 for neutral cards (7-9), and -1 for high cards (10-Ace). Players maintain a "running count" as cards are dealt. When the count is positive, more high cards remain in the shoe, favoring the player. When negative, low cards dominate, favoring the casino. Players adjust their bet sizes and playing decisions based on this count, increasing bets when the count is favorable.