Sex ratio is the proportion of males to females in a population. Studies of birth records for human beings and other animals indicate that many species have more individuals of one sex than of the other. Among human beings, for example, 106 boys are born for every 100 girls. In the adult population, however, women outnumber men because women, on the average, live longer. There are 107 males for every 100 females between 0 and 14 years of age. There are 81 males for every 100 females over 65 years of age.
