psyduck said:
Apparently the index assigned to double down is determined by when double down has higher advantage than not double - something I do not understand.
does the stuff in this link maybe help? :
http://www.blackjackincolor.com/truecount6.htm
whatever it's an interesting question. the question of doubling down with respect to advantage is a multifaceted one.
i guess i don't fully know the answer to your question but here are some thoughts on the matter.
a ploppy might double down all sort of ways to his disadvantage.
a pure basic strategy player will double down properly for someone who does not know the count. so he'd have a better advantage than the ploppy but not so good of an advantage as a card counting player who will double down according to a indices triggered by the count.
each case has improving degrees of decision making power.
even more advantage comes into play for the card counter who can knowingly bet higher by the count, all the while knowing that he will achieve more successful double downs over a certain range of counts.
it's the old story for card counting in that it affords the counter opportunities to bet higher when he has the knowledge that he's gonna have more successful double downs. that and knowing when successful insurance bets are gonna happen more often than not and knowing that more snappers are gonna present is where the money is made, hence an advantage. so to a great degree the advantage comes from knowledge about what's gonna happen, pure and simple. imagine the possibilities for a hole carder who has even more knowledge, hence advantage.
another facet of the question has to do with the old story of the plain and simple fact that the players can double down if the rules so state, the dealer can not. just as players get payed three to two for snappers, the dealer does not, ect.
probably went off on a tangent here and didn't answer your question, just some thoughts on the matter.