Why the Hi-low surrender index for single deck is 1.4?

I highly doubt this fact...
I tested myself so many time, and most of time when the TC exceeds 1.4, buying insurance is not profitable.
For instance, when 6,5,7 are dealt, TC becomes 2+, then there are 16 Ten value cards, and 33 non-Ten value cards remaining. Since Ten value cards haven't reach one-half of non-Ten value cards, I shouldn't buy insurance.
So when I play single deck, I'll buy insurance when the TC exceeds 2.0, and I don't even trust 2.0. It just because I think 1.4 seems too low to buy insurance.

I also doubt the 3.0 index for six deck game because I tried to examine myself, and lots of time it is not profitable to buy insurance when the TC exceeds 3.0.

Can someone explain to me the theory of insurance indexes? Thanks!

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In that case, taking insurance has no effect since the amount of Ten value cards are equal to one half the amount of non Ten cards.
I don't know how they calculated the 1.4 index, it seems too low. I'll keep my 2.0 index..

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Quote: WangSanJose

In that case, taking insurance has no effect since the amount of Ten value cards are equal to one half the amount of non Ten cards.
I don't know how they calculated the 1.4 index, it seems too low. I'll keep my 2.0 index..

Taking insurance actually *has* an effect - reduced variance. In the above case, you should insure your 20 or take even money on your blackjack.