Bsic card counting assigns a positive, negative, or null value to each card (2 through ace). As each card is dealt, the running count is adjusted by each card's assigned value. There are multiple card counting systems in use, but the Hi-Lo system, proposed by Harvey Dubner in 1963 and later refined by Julian Braun and Stanford Wong [3], is one of the more basic and illustrative systems.
In the Hi-Lo system the cards 2 through 6 are assigned a value of -1. Ten's (and face cards) through aces are assigned a value of +1. Cards 7, 8 and 9 have a value of zero (so they can be ignored).
For example, on a fresh shuffle, the count begins at zero. The dealer then deals the following sequence of cards: 5, 7, 2, Ace, 6, 3, 8, Jack. As each card comes out, the count is adjusted (starting at a count of zero). The adjustment values for the count would be -1 for 5, 0 for 7, -1 for 2, +1 for Ace, -1 for 6, -1 for 3, 0 for 8, +1 for Jack. As each card is delt the count is adjusted by the adjustment values. So the running count after each card is: -1, -1, -2, -1, -2, -3, -3, -2. So the final count, after this sequence of cards mentioned above is -2.
The Hi-Lo system is an example of a balanced card counting system. There are an equal number of +1 and -1 cards in the deck, so a count of all 52 cards would result in an end count of 0. The Hi-Lo system is also an example of a single level system, because cards are assigned only a single value, + or -1.[4]
The average deck always has a zero count, which is an advantage to the casino. Good counts are rare, only 25% of the time will the count usually favour the player. On average a counter will have a 1% edge, if they do not play or minimum bet when the count is bad, and increase their bets when the count is good. This means at a $10 table they would need to play, on average, 100 hands to make $10, which could be 2 hours of play or more.
The variance in blackjack is also very large. While they would win $10 on average for every 100 hands, it would take many thousands of hands to a have a high chance of being in profit. For this reason most casinos do not care about card counters who are playing $5 or $10 games. At a $25 table a good counter can make over $10 per hour (averaged over hundreds of hours), and many can make more than the dealer, which is an obvious problem for the casino. [citation needed]