The adult sex ratio and human population homeostasis.
About 50% of Swedish infants born in 1750 survived to have children themselves, and when they did they produced about 4 babies per family. In 1970 nearly all infants born could be expected to survive to adulthood, and about 2 babies were produced per family. This matching of the fertility rate to the childhood mortality rate could be the result of changes in the adult sex ratio.
D000367:Age Factors; D001723:Birth Rate; D005260:Female; D005298:Fertility; D006801:Humans; D008297:Male; D009026:Mortality; D011157:Population Dynamics; D012744:Sex Ratio; D013548:Sweden