Hi-Lo %

In reading �Professional BJ� by SW, The point is made that betting efficiency is 97% while playing efficiency is only 51%. It states: �All of these tables on deviating from basic strategy are of minor value.�
Does that mean when I have big bet out and thus vary from BS I only get the play right half the time? If so, why both with the variations from Basic Strategy?
[I�m a new counter and still working on my skills.]

51% is not the same as half. AP is all about the long run. In the long run, that extra 1% is well worth bothering with.

One % may not be worth much if too complex.
In �Blackbelt in BJ�, they ran some Sims using the index numbers in Pro BJ and found the numbers need not be so precise. He converted all original values to �1, +1 & +4. The results with the original index values and the new simplified values were equal. Thus from a practical $$ standpoint it does not matter when you simply the index values.
The largest gains are when you Wong out, not when you change BS

What it mean is:

If you were a computer knowing the exact composition of the remaining cards to be dealt, you would deviate from basic strategy in a way that you could call 100% efficient. This method would give you an extra edge over playing the same hand using Basic Strategy. Now, using Hi-Lo you will get 51% of this "computer best way to play".

why bother to post? Your original question wasn't about using simplified High-Low versus regular High-Low, but about High-Low versus some other stronger system. You will win up to 20% more money using a stronger system and a more complete set of index numbers than you will with a simplified version of High-Low....it depends on the game and the quality of it. There are, of course, other considerations, like what type of games do you most often play, how much added fatigue does a more advanced system generate, etc. But I would not say that anywhere from 5% to 20% in additional EV left on the table "may not be worth much". 5% may not be enough added win if you get mentally worn out 2x faster using halves than with High-Low.

That said, you are correct, Arnold Snyder has shown that by rounding index numbers within clusters to -1,+1,and +4 you will get most of the gain from the High-Low system...especially on shoes where betting is a more important strategy component.

Thanks GMan
Do I understand this correctly?
It is not 51% more accurate,
It is 51% of the increase in the additional edge.
Big difference

I was not trying to answer my own question.
I just felt the reduction in the number of index numbers
showed they were not all that significant.
I�m a new counter and reading all the books I can.

"It is 51% of the increase in the additional edge."

It is 51% of the "best possible play" if you knew the remaining composition of the pack.

Playing Efficiency vs. Betting Correlation:

In shoe games Betting Correlation dominates to the point where playing efficiency is of just monor importance.

In hand-held games Playing Efficiency is VERY important, which is why Hi-Lo is NOT a good choice for those games.

Counts like Hi-Opt II and Advanced Omega II have P.E.'s are around .67 and betting correlations of .98 - .99 -- but these counts are Level Two counts and require side-counting Aces and using 1/4 deck True Count computations.