Start with no children

repeat step

{

Every couple who is still having children has a child. Half the couples have boys and half the couples have females.

Those couples that have females stop having children

}

At each step you get an even number of males and females and the number of couples having children reduces by half (ie those that had females won't have any children in the next step)

So, at any given time you have an equal number of males and females and from step to step the number of couples having children is falling by half. As more couples are created the same situation reoccurs and all other things being equal, the population will contain the same number of male and females

Start with no children

repeat step

{

Every couple who is still having children has a child. Half the couples have males and half the couples have females.

Those couples that have females stop having children

}

At each step you get an even number of males and females and the number of couples having children reduces by half (ie those that had females won't have any children in the next step)

So, at any given time you have an equal number of males and females and from step to step the number of couples having children is falling by half. As more couples are created the same situation reoccurs and all other things being equal, the population will contain the same number of male and females