United States. Central Intelligence Agency, The 2005 CIA World Factbook
“ Sex ratio This entry includes the number of males for each female in five age groups - at birth, under 15 years, 15-64 years, 65 years and over, and for the total population. Sex ratio at birth has recently emerged as an indicator of certain kinds of sex discrimination in some countries. For instance, high sex ratios at birth in some Asian countries are now attributed to sex-selective abortion and infanticide due to a strong preference for sons. ”
