Most women do not want a career in STEM and nor do most men. Why should the small fraction of women who do want such a career be the same size as the small fraction of men? To put it another way, as long as everyone has the opportunity to pursue a STEM career, and as long as the selection process is fair, why would it be important to get as many women as men into jobs that fewer women want?

Although men and women are roughly equally represented in STEM overall, in certain fields, the sex ratios are somewhat unbalanced. More women than men are found in health-related fields, for instance, whereas more men than women are found in fields such as computer science, engineering, and physics.

[This] paper has two main aims. The first is to examine the evidence that factors other than workplace discrimination contribute to the gender gaps in STEM. These include relatively large average sex differences in career and lifestyle preferences, and relatively small average differences in cognitive aptitudes – some favouring males, others favouring females – which are associated with progressively larger differences the further above the average one looks. The second aim is to examine the evidence suggesting that these sex differences are not purely a product of social factors but also have a substantial biological (i.e. inherited) component.

[I]f we make the reasonable ballpark assumption that people working in a given field tend to come from the 25% of people most interested in that field, sex differences in occupational interests would account for the entirety of the engineering gender gap and much of the gap in science and mathematics.

[A]mong the minority of people who possess exceptional mathematical abilities, the women are more likely to possess exceptional language abilities as well. This means that mathematically gifted women have more vocational options than their male counterparts, and consequently that fewer mathematically gifted women end up pursuing a STEM career. To the extent that this explains the gender gap in maths-intensive fields, the gap results not from mathematically gifted women having fewer options, but rather from them having more.

Real-world data going back to the 1980s suggest that, although fewer women apply for jobs in fields such as maths, physics, chemistry, biology, and engineering, those who do apply are no less likely to be interviewed and no less likely to be offered the job. On the contrary, they are generally more likely to be.

Why should we put a statistical, collective goal – i.e., more equal sex ratios in STEM – above the happiness and autonomy of the flesh-and-blood individuals who constitute those collectives? Why should policy makers’ preference for gender parity take precedence over individual men and women’s preferences regarding their own careers and lives?

[W]e should strive to eliminate bias and barriers of every kind... What we would argue, though, is that even if this were achieved, STEM gender gaps would be unlikely to disappear given persistent sex differences in interests and other STEM-relevant traits – differences plausibly due in part to biological causes. The question, then, is: Would this necessarily be a problem? In our view, as long as unjust impediments are removed, and everyone is invited, it would not be. On the contrary, it would be unfortunate if, for all the talk of celebrating differences and diversity, we ultimately came to insist that justice requires sameness.

In the quest to promote women in STEM, academics and activists may sometimes inadvertently overstate the ubiquity of bias and discrimination against women in this sector. An unintended consequence may be to scare away some women who would otherwise be interested in a STEM career... If women are given the impression that the STEM workplace is a hotbed of sexism and an unwelcome place for women, many might quite understandably decide to look for other fields in which to make their mark.

Do women avoid fields like engineering because of the tendency of male-dominated fields to discriminate against women? Probably not. Prior to the women's movement, engineering was no more male-dominated than medicine and law. And women have entered medicine and law by the droves. When women enter male-dominated fields, they tend to enter the more glamorous occupations. And the media reinforces this. There was L.A. Law, but no L.A. Engineering. ER doesn't mean Engineering Room. Women receive six layers of encouragement to enter fields involving engineering, computers, and math and science: first, better starting salaries than men's; second, special programs for girls in high school; third, female-only government scholarships; fourth, female-only corporate grants and scholarships; fifth, the advertising that reaches out to women to create a more female-supportive atmosphere; and sixth, special grants for science programs at leading women's colleges.

Unconscious bias that women are less qualified than men to study or teach STEM disciplines still exists.

First, the claim is not that men perform better than women in every cognitive domain. On the contrary, men perform better in some domains whereas women perform better in others. The best-known examples are that men score higher than women on most tests of spatial ability, whereas women score higher than men on most tests of language ability, including verbal comprehension, reading, and writing... Second, even in areas where men do perform better, the claim is not that all men – or even most – perform better than all or most women. As with occupational preferences, members of both sexes vary enormously in every cognitive aptitude, and the distribution for men overlaps almost entirely with that for women. However, for some aptitudes, the distribution for one sex is shifted somewhat to the right of that for the other, such that the average score for the former is somewhat higher. In saying this, it’s worth stressing that the average score does not describe all members of the group, or even the typical member, but merely represents the central tendency within a broad array of scores. Most people fall above or below the average. Third, the claim is not that these cognitive sex differences are especially large. On the contrary, at the centre of the distribution, they tend to be quite small. The only reason they matter at all is that even small differences at the mean are associated with progressively larger differences the further from the mean one looks... Fourth, the claim is not that women lack the cognitive talents to make it in STEM. Most people lack the cognitive talents, and of those who do possess them, some are men and some are women.

It is generally recognized that women are better than men at languages, personal relations and multitasking, but less good at map-reading and spatial awareness. It is therefore not unreasonable to suppose that women might be less good at mathematics and physics. It is not politically correct to say such things....But it cannot be denied that there are differences between men and women. Of course, these are differences between the averages only. There are wide variations about the mean.

Sex differences in various psychological traits – in particular, average differences in career-related interests – contribute more to STEM gender gaps than is often assumed. These differences are not due solely to learning, but have a biological component as well... Certainly, the evidence for a biological contribution is not beyond criticism. We suggest, however, that the totality of the evidence renders the Nurture-Only view considerably less plausible than the Nature-Plus-Nurture alternative. The evidence we find most compelling includes the stubbornness of the sex differences over time, even despite efforts to eradicate them; the cross-cultural consistency of the differences; the early appearance of some differences during development; evidence linking the traits in question to prenatal hormonal exposure; and in some cases, comparable differences in evolutionarily relevant nonhuman animals. Each of these findings would be more surprising if the relevant sex differences were due solely to culture than if biology were also involved. And although alternative explanations for any particular finding are always possible, the convergence of these very different lines of evidence adds up to a strong prima facie case for a non-trivial biological contribution.