Key counts in the K-O system

[JHRainesJr]

I have been reading and practicing the strategy in K-O Blackjack and am just now moving to the counting system. One question on the counting is how were the key counts developed in this system. The authors never really develop the point, the key counts are simply given for various numbers of decks.

I believe that the key counts may be developed from a weighting system that looks back at the real value of removing cards from the pack (change in player expectation). When I use this method for a one deck game, it does yield a key count of +2. When applied to the 2 deck game, the answer is wrong, but that is probably because the real value of removing a particular card from the pack changes as the number of decks changes and the real values for 2 decks is not given in the book.

Does anyone know, is this the method used to the authors to develop the key counts in this system? I suppose, it doesn't really matter, just learn the key counts. However, I'm one of those people who just seems to remember things better if I understand the rationals involved. Or am just curious to an inordinate level and just want to know because I want to know!

 

[KenSmith]

IRC and Key Counts

From http://www.koblackjack.com (Archive copy)

Standard Initial Running Counts (IRCs) and Key Counts
1-deck IRC=0, Key=+2
2-deck IRC=-4, Key=+1
6-deck IRC=-20, Key=-4
8-deck IRC=-28, Key=-6

I don't remember how the Key numbers are derived, but if I recall correctly they are dependent on deck penetration as well, so they are chosen for 'typical' games.

The only precise number that KO can provide is the 'Pivot' count, which is when the player's advantage is equivalent to a Hi-Lo true count of +4.

At least, all these items are what I recall from memory. Re-reading KO might be a good idea for me, since these ideas are a little fuzzy!

I've always preferred balanced counts because of the imprecise nature of the information provided by unbalanced counts. However, for most players, I agree that the simplicity is worth the tradeoff.

 

[schismist]

simulation: can do better with little effort

I think the key count is based on simulation. They simulated a bunch of shoes and looked at the first running count that had a positive expectiation over all the hands, ignoring how many decks have been played.

The way I look at it: the number of sevens played is sort of a way to encode the number of decks that have been played, approximately. That is if you've seen four sevens, on average, 1 deck has been played.

Personally, when the running count is near the key count, I look over and approximate how many decks have actually been played. Then, with this unbalanced system, you can still get a rough idea of the true count without dividing.

For example, let's say we're playing 6-deck, and the count is at the key count of -4.

If only one deck has been played, then the running count would be, on average, -20+4=-16. I take this as a good sign that -4 is higher than -16 and increase my bet a little at the key count.

If, however, 4.5 decks have been played, the running count would be, on average -20+4.5*4=-2. This means that the actual running count is lower than the average running count, so I don't increase my bet here.

If you actually do the division:

With 1 deck played, TC = (-4 - (-16) ) / 5 = 12 / 5 = +2.4

With 4.5 decks played, TC = (-4 - (-2) ) / 1.5 = -2 / 1.5 = -1.3.

(btw, I customize the count to start at IRC=0) so I don't have to mess around with negatives when it matters.)

So in other words, with few decks played, increase your bet at the key count (or slightly lower). With several decks played, wait for the running count to get a little higher. Make sense?

 

[21forme]

At the pivot point, TC=+4, regardless of the number of decks. You're correct that TC at the key count varies. Personally, I use a customized key count based on the number of decks played. I derived the numbers from this thread:
http://www.blackjackinfo.com/bb/showthread.php?t=5732 .

Using an IRC = -3, I start bet ramping as follows:
1 deck +9
2 decks +11
3 decks +14
4 decks +16

Each of these is a TC=+1.5. Note that as you are deeper in the shoe, you should ramp your bets more quickly, as the TC rises more quickly (TC=+4 at RC=+20 in all cases) and my maximum bet is out at RC=+20.

One other note - the only index play at the key count is 16 v 10, the others occuring at the PP. I also use the adjusted key counts for this play when it occurs (much too often!)