In another thread, a question was asked about why the floating advantage happens and what the “mechanics” are behind it. The thread quickly devolved, without, I think, really helping the OP much. I’ve re-read the relevant sections of BJA3 and Griffin multiple times, and put a lot of thought into it, and I think I finally understand it myself, but I had to talk myself through it in a different, more explicit way than BJA3 or Griffin describe it. My explanation to myself may help others understand it as well.

Here goes:

First, I propose we define the Floating Advantage Theorem: “As the pack is depleted, the true count count indicating a given advantage decreases in the most common true counts.”

As to why this happens, here’s my best understanding:


  1. Average advantage is the same at all points in the pack; there is no inherent advantage change as the pack is depleted (some may want to read that again).
  2. True count is a tool to indicate and estimate advantage; it is not advantage unto itself.
  3. At very high and very low true counts, advantage *per true count* is lower than at moderate true counts (due to more pushes in very high true counts and poor double-down prospects in very low true counts)
  4. As the pack is depleted, very high and very low true counts become more common and the mean absolute value of the true count increases.
  5. As the pack depletes, very high and very low true counts become a larger fraction of all true counts. To maintain the same average advantage throughout the pack (refer to point #1 again), advantage per true count at more common true counts must rise to offset the lower advantage per true count at the now-more-common very high and very low true counts.
  6. Therefore, as the pack depletes, the true count *indicating* a given advantage must decrease at moderate true counts. These “moderate” true counts are approximately high-low -4 to +4 (by God!) as indicated in BJA3.


Throw out your corrections / improvements to what I’ve said, or, if it’s perfect as is, go ahead and inflate my ego. If I'm way off, enlighten me.