Card counting
Card counting is a blackjack strategy used to determine whether the player or the dealer has an advantage on the next hand.
"Card counter" redirects here. For the film, see The Card Counter.Card counter[edit]
Card counters are advantage players who try to overcome the casino house edge by keeping a running count of high and low valued cards dealt. They generally bet more when they have an advantage and less when the dealer has an advantage. They also change playing decisions based on the composition of the deck.
Running counts versus true counts in balanced counting systems[edit]
The running count is the running total of each card's assigned value. When using a balanced count (such as the Hi-Lo system), the running count is converted into a "true count", which takes into consideration the number of decks used. With Hi-Lo, the true count is the running count divided by the number of decks that have not yet been dealt; this can be calculated by division or approximated with an average card count per round times the number of rounds dealt. However, many variations of the true count calculation exist.[10]
Ranging bet sizes and the Kelly criterion[edit]
A mathematical principle called the Kelly criterion indicates that bet increases should be proportional to the player's advantage. In practice, this means that the higher the count, the more a player should bet to take advantage of the player's edge. Using this principle, a counter can vary bet sizes in proportion to the advantage dictated by a count. This creates a "bet ramp" according to the principles of the Kelly criterion. A bet ramp is a betting plan with a specific bet size tied to each true count value in such a way that the player wagers proportionally to the player's advantage to maximize bankroll growth. Taken to its conclusion, the Kelly criterion demands that a player not bet anything when the deck does not offer a positive expectation; "Wonging" implements this.[14]
Historically, blackjack played with a perfect basic strategy offered a house edge of less than 0.5%. As more casinos have switched games to dealer hits soft-17 and blackjack pays 6:5, the average house edge in Nevada has increased to 1%. A typical card counter who ranges bets appropriately in a game with six decks will have an advantage of approximately 1% over the casino. Advantages of up to 2.5% are possible at normal penetrations from counting 6-deck Spanish 21, for the S17 or H17 with redoubling games.[15] This amount varies based on the counter's skill level, penetration (1 – a fraction of pack cut off), and the betting spread (player's maximum bet divided by minimum bet). The variance in blackjack is high, so generating a sizable profit can take hundreds of hours of play. The deck will only have a positive enough count for the player to raise bets 10%-35% of the time depending on rules, penetration, and strategy.[16]
At a table where a player makes a $100 average bet, a 1% advantage means a player will win an average of $1 per round. This translates into an average hourly winning of $50 if the player is dealt 50 hands per hour.
Under one set of circumstances, a player with a 1-15 unit bet spread with only one-deck cut off of a six-deck game will enjoy an advantage of as much as 1.2% with a Standard Deviation of 3.5 on a 2.1 unit average bet.[17] Therefore, it is highly advisable for counters to set aside a large dedicated bankroll; one popular rule of thumb dictates a bankroll of 100 times the maximum bet per hand.[18][19]
Another aspect of the probability of card counting is that, at higher counts, the player's probability of winning a hand is only slightly changed and still below 50%.[20] The player's edge over the house on such hands does not come from the player's probability of winning the hands. Instead, it comes from the increased probability of blackjacks, increased gain and benefits from doubling, splitting, and surrender, and the insurance side bet, which becomes profitable at high counts.
Many factors affect expected profit, including:
Legal status[edit]
Card counting is not illegal under British law, nor is it under federal, state, or local laws in the United States provided that no external card counting device or person assists the player in counting cards. Still, casinos object to the practice, and try to prevent it,[21][22] banning players believed to be counters. In their pursuit to identify card counters, casinos sometimes misidentify and ban players suspected of counting cards even if they do not.[23]
Atlantic City casinos in the US state of New Jersey are forbidden from barring card counters as a result of a New Jersey Supreme Court decision. In 1979, Ken Uston, a Blackjack Hall of Fame inductee, filed a lawsuit against an Atlantic City casino, claiming that casinos did not have the right to ban skilled players. The New Jersey Supreme Court agreed,[24] ruling that "the state's control of Atlantic City's casinos is so complete that only the New Jersey Casino Control Commission has the power to make rules to exclude skillful players." The commission has made no regulation on card counting, so Atlantic City casinos are not allowed to ban card counters. As they are unable to ban counters even when identified, Atlantic City casinos have increased the use of countermeasures.[25]
Macau, the only legal gambling location in China,[26] does not technically prohibit card counting but casinos reserve the right to expel or ban any customers, as is the case in the US and Britain.[27] The use of electronic devices to aid such strategies, however, is strictly prohibited and can lead to arrest.[28]
Casino reactions[edit]
Detection[edit]
Monitoring player behavior to assist with detecting the card counters falls into the hands of the on-floor casino personnel ("pit bosses") and casino-surveillance personnel, who may use video surveillance ("the eye in the sky") as well as computer analysis, to try to spot playing behavior indicative of card counting. Early counter-strategies featured the dealers learning to count the cards themselves to recognize the patterns in the players. Many casino chains keep databases of players that they consider undesirable. Casinos can also subscribe to databases of advantage players offered by agencies like Griffin Investigations, Biometrica, and OSN (Oregon Surveillance Network).[29] Griffin Investigations filed for Chapter 11 bankruptcy protection in 2005 after losing a libel lawsuit filed by professional gamblers.[30] In 2008 all Chapter 11 payments were said to be up to date and all requirements met, and information was being supplied using data encryption and secure servers.[31] If a player is found to be in such a database, they will almost certainly be stopped from play and asked to leave regardless of their table play. For successful card counters, therefore, skill at "cover" behavior, to hide counting and avoid "drawing heat" and possibly being barred, may be just as important as playing skill.
Detection of card counters will be confirmed after a player is first suspected of counting cards; when seeking card counters, casino employees, whatever their position, could be alerted by many things that are most common when related to card counting but not common for other players. These include:[32][33][34]