6.7.txt

It should be 1 to 1.

Chance of having a son: S = 1/2
Chance of having a daughter: S = 1/2

The expected number of daughters per couple is 1.

The expected number of sons per couple is:

0 sons: D = 1/2
1 son: S * D = 1/4
2 sons: S * S * D = 1/8
3 sons: S * S * S * D = 1/16
...
k sons: S ^ k * D = 1/2^(k+1)

Infinite sum: 1/2 + 1/4 + 1/8 + ... = 1.

So, the expected gender ratio is 1 daughter to 1 son.

In fact, the ratio should be the same even if the strategy is reversed (keep having daughters until having a son), for the same argument.