Gray E, Morgan D K
J Hered. 1976 Sep-Oct;67(5):319-21. doi: 10.1093/oxfordjournals.jhered.a108742.
During 1975, data were obtained from 1016 unmarried Caucasian students on their preference for family size, combination of sexes within the desired size, and permutation of sexes within the desired combination. The most desired family size by both female and male respondents was two children, but the average size was more than 2.46 children. Combinations involving both sexes of children were preferred over single sexes in all families of two or more children. The preference for the first-born to be male was consistent in all combinations of male and female children. Considering all desired family sizes and combinations of sexes of children the resulting sex ratio was 137.9 males:100 females.