Daughter
In the United States, the birth rate is 105 sons to 100 daughters which has been the natural birth rate since the 18th century. About 80 percent of prospective adoptive parents from the US will choose a girl over a boy. In fertility clinics that enable sex preferences, daughters are usually preferred over sons. In the traditions of various Abrahamic religions, Luluwa is regarded as the first daughter to have ever existed.
Human sex ratio
Several studies have examined human birth sex ratio data to determine if there is a natural relationship between the age of mother or father to the birth sex ratio. For example, Ruder has studied 1.67 million births in 33 states in the United States to discern effect of parent's age and birth sex ratios. Similarly, Jacobsen et al. have studied 0.82 million births in Denmark with the same goal. These scientists find that maternal age has no statistically significant role on human birth sex ratio. However, they report a significant effect of paternal age. Significantly more male babies were born per 1000 female babies to younger fathers than to older fathers. These studies suggest that social factors such as early marriage and quickly fertile couples may play a role in raising birth sex ratios in certain societies.