How common are intersex traits?
It’s not easy to determine how many people are born with an intersex variation.
How common are intersex traits? According to the American Psychological Association,
"There is no simple answer to this question. Intersex conditions are not always accurately diagnosed, experts sometimes disagree on exactly what qualifies as an intersex condition and government agencies do not collect statistics about intersex individuals” (American Psychological Association, 2006).
Some experts believe it’s important to include subtle variations in our bodies, such as mild hypospadias, a condition in which a male’s urethral opening is located on the underside of his penis, rather than at the tip. Others limit the definition if intersex to congenital variations in which chromosomal, gonadal, or anatomical sex is more noticeably atypical (Ainsworth, 2006). While estimates vary from 1 in 100 to 1 in 4500, a commonly cited range is 1 in 1500-2000.
Check out this article in the journal Nature for an interesting discussion of ongoing debates about what qualifies as intersex.
Ainsworth, C. (2015). Sex redefined: The idea of two sexes is simplistic. Biologists now think there is a wider spectrum than that. Nature, 518,288-291. https://www.nature.com/news/polopoly_fs/1.16943!/menu/main/topColumns/topLeftColumn/pdf/518288a.pdf
APA Task Force on Gender Identity, Gender Variance, and Intersex Conditions (2006). Answers to your questions about individuals with intersex conditions [Pamphlet]. American Psychological Association. https://www.apa.org/topics/lgbt/intersex.pdf