India, China and Asia as a whole has this practice of preference of male child.
Found someone did excellent math on this
If we call the current number of women the population size P, the number of boys B that will be born is P as well - one boy for every mother.
Consider the number of girls in a family, we'll call this G. The higher G, the fewer families there are with this amount of daughters:
G Fraction of families with exactly G daughters
0 1/2 (the families whose first child is a boy)
1 1/4 (second child is a boy)
2 1/8 (etc.)
3 1/16
4 1/32
5 1/64
. etc.
.
Summing over all G, we find the total number of daughters H:
H = sum( fraction of families * number of daughters in family )
= sum((1 / 2^(G+1)) * G) * P with G from 0 to infinity.
sum((1 / 2^(G+1)) * G) with G from 0 to infinity equals one, so the number of girls is also equal to the population size P.
Of course letting G approach infinity requires P to approach inifinity as well, but we are interested in the fraction of daughters.
You may object that in practice, women will of course not have a near-infinite amount of children. Let's say all women call it quits after 5 daughters. In that case the G=5 families are 1/32 of the population, just like the G=4 ones. Manual summation gives us 31/32, so
G = 31/32 * P
The number of boys is also reduced; 1 out of 32 women never has a boy, so the number of boys B is also
B = 31/32 * P
Credit to https://www.quora.com/profile/Jelle-Nauta
