[Originally published in the Summer 2015 issue of American Astronomical Society (AAS) Committee on the Status of Women in Astronomy (CSWA) Status newsletter (p. 15-17). If you quote this article in any way, please cite the version in Status. Many thanks to Nancy Morrison and Joannah Hinz for editing assistance.]
Suppose that two astrophysicists with similar education, experience, and accomplishments—let’s call them Dr. X and Dr. Y—apply for a tenure-track faculty position. If Dr. X is female and Dr. Y is male, and if the selection committee members have conscious or unconscious gender bias, then, unfortunately, one might expect it to be more likely that Dr. Y would be offered the position.
But a controversial and influential new paper argues the opposite. In the title of their April 2015 article in the Proceedings of the National Academy of Sciences (PNAS), Wendy M. Williams and Stephen J. Ceci, both psychologists and full professors at Cornell University, claim, “National hiring experiments reveal 2:1 faculty preference for women on STEM tenure track.” 
The authors base their conclusions on five randomized, controlled experiments at 371 U.S. colleges and universities in biology, engineering, economics, and psychology. In these experiments, tenure-track faculty members evaluated the biographical summaries or the curricula vitae of fictitious faculty candidates—including one “foil” candidate—mostly with impressive qualifications but with different genders and different life situations, such as being a single parent or having taken parental leave.
Their analysis reveals an unexpected result: faculty reviewers strongly preferred female candidates to male ones by a highly significant 2:1 advantage. Williams and Ceci conclude, “Efforts to combat formerly wide-spread sexism in hiring appear to have succeeded. After decades of overt and covert discrimination against women in academic hiring, our results indicate a surprisingly welcoming atmosphere today for female job candidates in STEM disciplines, by faculty of both genders.”
The article received considerable media attention from a variety of outlets. In particular, Nature, The Washington Post, The Economist, and Inside Higher Ed reviewed the article without much skepticism. Presumably, the authors’ claim that sexism no longer exists and gender bias is a thing of the past is a message that many people want to hear. On 31 October 2014, Williams and Ceci published an op-ed in The New York Times entitled, “Academic Science Isn’t Sexist,” in which they presented a shorter version of the same argument. 
On the other hand, Lisa Grossman in New Scientist  and Matthew Francis in Slate  analyzed the study in more detail and expressed more criticism. Both authors outlined the flaws in the analysis by Williams and Ceci. The experimental evaluations in their study involved only reviews of candidates’ biographies, without all the other activities that normally enter into faculty hiring and that may be affected by gender bias: personal interviews, presentation of talks, social events with potential colleagues, and determination of a short list by a selection committee. These simplified experiments do not accurately represent a real hiring process.
Many other studies and and a wealth of anecdotal evidence contradict the conclusions of Williams and Ceci. For example, Viviane Callier, Ph. D., contractor at the National Cancer Institute, told us  that recent surveys [6,7] found evidence of pervasive sexism in letters of recommendation—a domain in which the assumption of a level playing field does not apply and which is out of the woman applicant’s control. Moreover, faculty hiring is dominated by graduates of a few prestigious institutions and labs that are disproportionately headed by men, who are more likely to hire other men. “To imply, like Williams and Ceci, that ‘we are done,’ or that ‘the problem is solved,’ does a great disservice to the scientific community,” Callier said.
In any case, analysts agree that the underrepresentation of women in STEM fields is an ongoing problem. According to a National Science Foundation study in 2008, 31% of full-time science and engineering faculty are women. This fraction varies among different fields, however. In an American Institute of Physics survey , the representation of women among physics faculty members reached 14% in 2010, and for astronomy-only departments, it was 19%. Similarly, a 2013 CSWA survey of gender demographics  found that 23% of faculty at universities and national research centers are women. These fractions demonstrate improvement in recent decades, but clearly much more work needs to be done.
Furthermore, although women outnumber men among college and university graduates, men continue to dominate the physical sciences, math, and engineering. At higher levels of academic careers, the gender demographics worsen, in what is often described as a “leaky pipeline.” Women constitute only one third of astronomy graduate students and less than 30% of astronomy postdoctoral researchers. In addition to the underrepresentation of women, gender inequality persists in other areas as well: according to a report by the Institute for Women’s Policy Research , although women now pursue graduate degrees at the same levels as men, women with such degrees earn no more than 70% of their male colleagues, a larger divide than the overall pay gap.
“Unconscious bias” against women in science and math is not unique to men. In a 2012 PNAS study , Corinne A. Moss-Racusin and her Yale University colleagues found that female faculty are just as biased as men against female scientists. When people assess students, hire postdocs, award fellowships, and hire and promote faculty, biases propagate through the pipeline. Contrary to the conclusions of Williams and Ceci, the problem is on both the supply side and the demand side.
What can be done to address such biases? As difficult as it may be, if scientists simply acknowledge that we all carry some inner biases, those biases may be reduced. Meg Urry argued in the January 2014 issue of Status  that people who are aware of bias tend be more careful about how they make hiring decisions. In addition, increasing the fraction of women in hiring pools and in search committees helps to reduce unconscious bias as well.
Some institutions have National Science Foundation-funded ADVANCE Programs to increase the representation and advancement of women in STEM careers. The University of Michigan’s program , for example, includes efforts to develop equitable faculty recruitment practices, increase the retention of valued faculty, improve the departmental climate and work environment, and develop encouraging leadership skills of faculty, staff and students. Their program could be emulated at other institutions.
Finally, other important issues relate to gender bias and underrepresentation of women, including improving maternal and paternal leave policies, increasing access to child care, developing dual-career policies, promoting work-life balance, and reducing gender inequality of housework. Furthermore, other forms of underrepresentation are also important, and workers in STEM fields continue to strive to improve diversity in race, class, and sexual orientation, as well as gender.
 Williams, W. M., & Ceci, S. J. 2015, “National hiring experiments reveal 2:1 faculty preference for women on STEM tenure track,” PNAS, 112, 5360n
 Williams, W. M., & Ceci, S. J. 2014 October 31, “Academic Science Isn’t Sexist,” New York Times
 Grossman, L. 2015 April 17, “Claiming sexism in science is over is just wishful thinking,”
 Francis, M. R. 2015 April 20, “A Surprisingly Welcome Atmosphere,” Slate
 Callier, V. 2015, personal communication by email
 McNutt, M. 2015, “Give women an even chance,” Science, 348, 611
 Madera, J. M., Hebl, M. R., and Martin, R. C. 2009, “Gender and Letters of Recommendation for Academia: Agentic and Communal Differences,” Journal of Applied Psychology, 94, 1591
 Ivie, R., White, S., Garrett, A., & Anderson, G. 2013, “Women Among Physics & Astronomy Faculty: Results from the 2010 Survey of Physics Degree-Granting Departments,” American Institute of Physics
 Institute for Women’s Policy Research 2015, “The Status of Women in the States: 2015 Employment and Earnings”
 Hughes, A. M. 2014 January, “The 2013 CSWA Demographics Survey: Portrait of a Generation of Women in Astronomy,” Status, p. 1
 Moss-Racusin, C. A., Dovidio, J. F., Brescoli, V. L., Graham, M. J., & Handelsman, J. 2012, “Science faculty’s subtle gender biases favor male students,” PNAS, 109, 16474
 Urry, C. M. 2014 January, “Why We Resist Unconscious Bias,” Status, p. 10
 University of Michigan, ADVANCE Program