Female Fraction

Puzzle: There’s a certain country where everybody wants to have a son. Therefore each couple keeps having children until they have a boy; then they stop. What fraction of the population is female?

To be clear, we’re not asking, “What’s the average number of females in a family?” This is not asking per family. It’s asking, in the whole country, what’s the fraction of females to persons?

And since any specific instance of a country will have an unknown fraction (because of statistical variance), we’re really asking, “What is the expected fraction.” If you had a million universes, and computed the fraction of females to persons in each, and averaged the answers, what would you get?

~ See all puzzles ~