Without the interference of non-natural factors, the ratio of boys to girls at birth generally stays at roughly 105: 100. But because the death rate during childhood is slightly higher for boys than for girls, by adulthood the numbers of men and women are very close.
在自然情況下，新生兒男、女的比例通常維持一百零五比一百左右，由於男嬰夭折率略高於女嬰，成年後男、女比例相當接近。