Asexuals are currently thought to make up around 1–4% of the population. As with other sexual orientations though, it's difficult to get a precise idea of the prevalence of asexuality. This is due to studies relying to self-report data, and some issues more specifically related to asexuality as mentioned below.
Scientific studies that have been conducted on the prevalence of asexuality have tended to find that around 1% of the population is asexual [1–6]. It's likely, however, that the figures from these kinds of study are underestimates of the actual prevalence of asexuality. Some of the reasons for this are listed below.
- Due to the fact that the orientation is mostly invisible in the popular consciousness, most studies that look into this question will involve participants learning of the term/orientation for the first time while they are being surveyed.
- For the same reason it is likely that there are many people are asexual without realising it.
- One of these studies  found the rate of same-sex attraction (i.e. homosexuals plus bisexuals) to be around 1%, which is known to be an underestimate of the prevalence of same-sex attraction. This indicates that this kind of methodology may underestimate the rate of asexuality as well.
- As noted in , those with less sexual experience are less likely to participate in such surveys in the first place (and asexuals tend to have less sexual experience).
- Most studies into the prevalence of asexuality use a very restrictive definition of the term – usually along the lines of "have never experienced sexual attraction".
To elaborate somewhat – this kind of restrictive definition excludes those whose orientation has changed over time, and it excludes everyone in the space between "never" and allosexuality. Both are groups of people who might much more closely identify with asexuality than allosexuality. In addition, such studies often do not define what is meant by "sexual attraction" in the first place. This is problematic because it's common for asexuals, before they identify as such, to believe they're feeling sexual attraction because they are mislabelling romantic, sensual, or platonic attraction.
A more recent GLAAD survey reported that among under 35s the percentage of asexuals is 4% . This is in part due to the GLAAD survey using self-identification with asexuality rather than the more restrictive definition discussed above. It therefore includes people who are under the asexual umbrella but aren't strictly asexual (e.g. demisexuals). The lower age bracket of under 35s is also likely to mean that participants where more likely to be aware of asexuality before taking the survey.
Studies that look into the prevalence of different genders among the asexuality commonly find that the number of men is low compared to women [1,17]. In fact in some cases the number of men is even less than those that identify as neither men nor women . The reason for this is not well understood at present. At least part of the answer could be that men face greater barriers to identifying as asexual (or more specifically, identifying as not experiencing attraction) than other genders. For example:
- Men may feel more pressure to be overtly sexual, or they may be more likely to mistake romantic/sensual attraction for sexual attraction based on a cultural assumption that all men are sex-seeking.
- Men may be more likely to mistake outward signs of arousal (e.g. an erection) as necessarily indicating sexual attraction is present.
- Asexual men are as likely to masturbate as allosexual men, whereas asexual women are less likely to masturbate than allosexual women.1 This could disproportionately prevent men from identifying as asexual based on the false belief that asexuals do not masturbate.
However, since sexual orientation is a result of the complex interplay between environmental and genetic factors, it's possible that men are genuinely less likely than women to be asexual. For example, it is already known that men are more likely to be exclusively homosexual than to be bisexual, whereas women are more likely to be bisexual than to be exclusively homosexual [9–11]. From an evolutionary perspective, sexual behaviour is precisely the area in which we might expect a difference between the sexes, so it would not be surprising if it turned out that men are in fact less likely to be asexual than women.
Current estimates from the 2016 Asexual Community Survey  have the following breakdown.
- woman (63.0%),
- 'none of the above' (26.0%),
- man (10.9%).
An important caveat to the Ace Community Survey figures is that they are subject to sample bias (being administered by word-of-mouth on the internet) and they only include people that self-identify as ace (so they could be affected by a barrier to men identifying as ace compared to women).
One piece of evidence that asexuality is a distinct orientation comes from biomarkers associated with it – in a similar way to there being biomarkers associated with other non-hetero sexualities . Below you can find discussion of some of these biomarkers that have been observed in asexuals, as well as comparison to other non-hetero sexualities. Of course, it should be noted that these are characteristics of the entire population of asexuals (within which there is substatial variation) and not of individuals. Some effects may also be statistically significant while having a small magnitude.
Studies have found a few physical characteristics to be more prevalent among asexuals. These include being shorter [1,2] and weighing less than non-asexuals , as well as asexual women being more likely to have a later onset of menarche [1,2]. Evidence also suggests that asexuals are more likely to have poor health .
Asexuals are significantly more likely not be righthanded compared to heterosexuals, with a prevalence of over 25% . This same effect of being less likely to be right-handed is found among homosexual individuals . The evidence suggests that asexual men are more likely to not be righthanded even compared to homosexual men .
Fraternal birth order
There is statistically significant evidence that righthanded asexual men have more older brothers than righthanded heterosexual men; and that asexual women have fewer older brothers than heterosexual women . Among men, the number of older brothers born of the same mother has been associated with an increased likelihood of being homosexual [15,16]. (The same pattern is not found in women and may only apply to righthanded men .) Homosexual and asexual men and women are each more likely to have fewer older sisters than their heterosexual counterparts .
- See Can I be asexual if I masturbate? for more details.
- : Bogaert, Anthony F. (11 October 2012). Asexuality: Prevalence and associated factors in a national probability sample. The Journal of Sex Research. 41 (3): 279–287. doi:10.1080/00224490409552235.
- : Bogaert, Anthony F. (2013). The Demography of Asexuality. International Handbook on the Demography of Sexuality. Springer Netherlands: 275–288. doi:10.1007/978-94-007-5512-3_15.
- : Wellings, K. (1994). Sexual Behaviour in Britain: The National Survey of Sexual Attitudes and Lifestyles. Penguin Books.
- : Bogaert, Anthony F. (2006). Toward a conceptual understanding of asexuality. Review of General Psychology. 10 (3): 241–250. doi:10.1037/1089-26126.96.36.199
- : Greaves, Lara M.; Barlow, Fiona Kate; Lee, Carol H. J.; Matika, Correna M.; Wang, Weiyu; Lindsay, Cinnamon-Jo; Case, Claudia J. B.; Sengupta, Nikhil K.; Huang, Yanshu; Cowie, Lucy J.; Stronge, Samantha; Storey, Mary; De Souza, Lucy; Manuela, Sam; Hammond, Matthew D.; Milojev, Petar; Townrow, Carly S.; Muriwai, Emerald; Satherley, Nicole; Fraser, Gloria; West-Newman, Tim; Houkamau, Carla; Bulbulia, Joseph; Osborne, Danny; Wilson, Marc S.; Sibley, Chris G. (29 September 2016). The Diversity and Prevalence of Sexual Orientation Self-Labels in a New Zealand National Sample. Archives of Sexual Behavior. 46 (5): 1325–1336. doi:10.1007/s10508-016-0857-5
- : Accelerating Acceptance 2017. Harris Poll survey of Americans conducted on behalf of GLAAD.
- : Caroline Bauer et al (2018). 2016 Asexual Community Survey Summary Report, p. 16. Asexual Community Survey Team.
- : Bailey, J. Michael; Vasey, Paul; Diamond, Lisa; Breedlove, S. Marc; Vilain, Eric; Epprecht, Marc (2016). Sexual Orientation, Controversy, and Science. Psychological Science in the Public Interest. 17 (2): 45–101. doi:10.1177/1529100616637616. PMID 27113562.
- : LeVay, Simon (2017). Gay, Straight, and the Reason Why: The Science of Sexual Orientation. Oxford University Press. pp. 8–9. ISBN 9780199752966.
- : Balthazart, Jacques (2012). The Biology of Homosexuality. Oxford University Press. pp. 9–10.
- : Brotto, Lori A.; Yule, Morag (19 August 2016). Asexuality: Sexual Orientation, Paraphilia, Sexual Dysfunction, or None of the Above?. Archives of Sexual Behavior. 46 (3): 619–627. doi:10.1007/s10508-016-0802-7.
- : Yule, Morag A.; Brotto, Lori A.; Gorzalka, Boris B. (18 September 2013). Biological Markers of Asexuality: Handedness, Birth Order, and Finger Length Ratios in Self-identified Asexual Men and Women. Archives of Sexual Behavior. 43 (2): 299–310. doi:10.1007/s10508-013-0175-0.
- : Lalumière, Martin L.; Blanchard, Ray; Zucker, Kenneth J. (2000). Sexual orientation and handedness in men and women: A meta-analysis. Psychological Bulletin. 126 (4): 575–592. doi:10.1037/0033-2909.126.4.575.
- : Blanchard, Ray (January 2008). Review and theory of handedness, birth order, and homosexuality in men. Laterality: Asymmetries of Body, Brain and Cognition. 13 (1): 51–70. doi:10.1080/13576500701710432.
- : Blanchard, Ra, & Bogaert, Anthony F. (1996). Homosexuality in men and number of older brothers. American Journal of Psychiatry. 153 (1): 27–31. January 1996. doi:10.1176/ajp.153.1.27.
- : Kinsey, Alfred C. (1953). Sexual Behavior in the Human Female. W.B. Saunders. ISBN 978-0-253-33411-4.