Balanced vs. unbalanced card count
Balanced counting systems
Most professional card counting systems are balanced. Using a card counting system, card counter attributes points - positive or negative - to different cards depending on how useful the card may prove for the player. The system becomes balanced when the number of positive and negative point values is equal and the total sum of these points equals zero.
Running count and true count
The players applying balanced blackjack counting systems adds the point values of cards in play to his or her "running count". "Running count" is in fact counting the total of all point values of the cards tracked in play starting from the last deck shuffle. For example, with count started at zero, 3 low cards dealt with point value of +1 and 2 high cards dealt with point value of -1, the player's "running count" makes +1 (3-2 equals 1).
"Running count" works efficiently in single-deck blackjack. But as soon as it comes to defining the amount of your bets and making decisions to play your hand, the "running count" is to be converted into the "true count", which is seen as a more advanced card counting technique taking into account the number of decks in play. For example, with the balanced Hi-Lo system, "true count" is actually "running count" divided by the number of the decks that yet remain to be dealt. Applying "true count" proves to be quite difficult to most players, especially as the player is supposed to memorize all decisions according to the certain basic blackjack strategy.
Unbalanced card counting systems
The complexity of systems based on "true count" has made necessary the development of simpler unbalanced systems that don't require conversion into "true count".
According to unbalanced Noir ten count system, the sum of positive and negative point values is not equal and doesn't make a zero. All 10-valued cards here are assigned point value of -2, whereas other cards including Aces get the point value of +1. The inequality of card values in unbalanced count does not require the conversion into "true count" to define necessary player decisions while playing blackjack, which means that the players only need to keep their "running count".
The unbalanced ten count system is also useful at defining the odds for insurance. With the running count of +4, the ratio of 10-valued cards to other cards makes exactly 2 to 1, which means it is possible to make insurance bets.
Unfortunately, unbalanced card counting systems are much less accurate than the more complex balanced systems as they trace the cards that have already been dealt, without defining any fluctuations for games with different number of decks in play. Besides, unbalanced systems offer rather small betting efficiency meaning that "running count" does not help to define the optimal amount of the bet.