by Norm Wattenberger

Splits, Doubles, Blackjacks, Insurance

How does the count affect Splits, DD's, BJs and Insurance?

Now let us look at some hand types. The percentage of hands that are splits, doubles, insurance and Blackjacks is charted by card count. Each of these types is affected differently by the count. In this chart, over 100 indexes are used. We see double downs in green. The percentage of hands doubled increases as more and more double down indexes are reached. This happens only if you use many indexes as we will see later. At about a true count of +5, double downs start declining. This is because the large number of high cards at high counts reduces the possibility of a DD opportunity. Splits, displayed in red, also increase as more and more indexes are reached. Blackjacks, in cyan, increase substantially as the count increases and this is very important to overall gain. Insurance, in blue, does not exist below the Insurance index. It then appears and gradually increases in percentage of hands as the number of tens and aces increases.


How is this affected by indexes?

This chart looks very different. Here a comparison is made between full indexes (100+) and no indexes. Blackjacks and Insurance have been removed. The green line is the same as in the above chart, percentage of hands doubled with full indexes. The cyan line shows the hands doubled when there are no indexes. The lines are completely different. Without indexes the cyan line starts very high and drops substantially as the count increases. This is because there are many low cards available at low counts, both for the dealer's upcard and for your own hand, allowing many doubles. As the count increases low cards are less common. But, many of these doubles are a mistake at low counts since you will probably also draw a low card and the dealer will probably not bust. So the indexes save you from doubling when you shouldn't at low counts. The green and cyan lines cross about true count zero. Here there are fewer low cards making fewer of the more common doubles available. But more indexes have been reached identifying more opportunities. These opportunities, like 9 vs. 7 are now available because the large number of high cards increases the likelihood that you will win the hand. Splits displayed in red for 100+ indexes and blue for no indexes behave in much the same manner. However, keep in mind that the very large-magnitude indexes are rare and we should not be playing at the very low indexes.

Sim details

  • Six decks, S17, DAS, LS, 4.81/6, Hi-Lo max indexes, trunc, half-deck
  • Ten billion rounds for six and two decks, five billion rounds for single-deck


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