Sixteen years.

That’s how long it will take before the number of women on scientific papers is equal to the number of men.

Luke Holman from the University of Melbourne got that estimate by working out the number of female and male authors on almost 10 million academic papers, published over the last 15 years. With help from Melbourne colleagues Cindy Hauser and Devi Stuart-Fox, he then used the data to estimate the size of the well-documented gender gap in science, and more importantly, how long it might take to close.

At the current rate of change, women will catch up to men in 16 years—but that overall estimate masks a huge amount of variation. For example, out of the 115 disciplines represented in the data, women authors outnumber men in just a handful (including nursing and midwifery) and publish at the same rate in just 23 (including psychology, nutrition, and public health).

In 87 of the 115 disciplines, women are still significantly outnumbered by men. Some of these, including anthropology, microbiology, and medical genetics, will reach parity within the next decade. But others, like physics, mathematics, and computer science, not only have the highest male biases, with women being outnumbered by a factor of six, but also the slowest rates of improvement. In physics, the gender gap might take 258 years to fully close. If nothing changes, no living physicist or mathematician will see parity within their lifetime—or their grandchildren’s.

“This goes against any false security that we are doing ‘enough,’ and we—society, institutions, and countries—have to do more if we are going to increase the rate of change,” says Kelly Ramirez, a cofounder of 500 Women Scientists.

At least 61 other studies have estimated the gender ratio of authors on academic papers, but most of these relied on people poring over papers by hand. Instead, Holman downloaded 9.15 million articles from PubMed, one of the largest repositories for medical and life sciences, and another half-million articles from ArXiv, which stores papers in mathematics, physics, astronomy, and more. He then wrote a program that used an online database to deduce the gender of every author. (He chose to exclude gender-ambiguous names like Jamie or Robin; that still left 92 percent of the data set and didn’t appreciably change the final estimates.)

The results give a sense of the gender gaps in science, but Holman cautions that even when parity in publishing is reached, that shouldn’t be seen as evidence that sexism has been banished. “Just because the data say that biology is at 40 percent women, it doesn’t mean that those women aren’t facing major gender challenges in their workplaces,” he says.

For example, his team found that in almost all fields, women are substantially less likely to be the last author on a paper—the spot that’s usually occupied by senior figures in leadership roles. Instead, relative to the overall gender ratio, they’re significantly overrepresented in the first-author position, which is usually occupied by junior researchers who do the bulk of the work. This speaks to a broader trend: The further up you go in academia, the more underrepresented women are. Indeed, Holman calculates that to close the gender gap at a senior level across all fields, it will take a median of 38 years, rather than just 16.

Demographic studies suggest that the gap doesn’t just exist because there were fewer women graduates in the past, and things haven’t caught up yet. Instead, the personal experiences of countless women and the results from a growing body of studies point to a raft of more likely explanations.

Women in science are less likely to be trained by elite laboratories, especially those run by men. They are paid less. Compared to men of equal skill, they receive less mentoring, they are more rarely invited to give talks, they are seen to be less competent and less employable, and their work is judged more harshly. On top of that, they must contend with stereotypes about their intelligence and scientific acumen, and significant levels of harassment and abuse. For each of these well-documented reasons, many women leave STEM careers early, while those who stay end up with fewer papers to their name than their male peers. And when they do publish, their work is less likely to be cited.

Even in fields with many women, inequality persists. For example, Holman found that across different disciplines, the most prestigious journals were also those with the fewest women authors. In some of the most famous journals, like Nature and The New England Journal of Medicine, women were underrepresented as senior last authors, and also comparatively rarer among the junior first authors.

Partly, that’s because prestigious journals often invite scientists to submit papers to them; Holman calculated that such invitations are extended to men twice as often as to women. It’s also possible that women submit a lower proportion of their papers to these top-tier journals, either through lack of confidence or lack of support. And it might be that peer-reviewers and editors are biased against women, whether implicitly or explicitly. “I have had a hell of a time publishing the majority of my papers, including ones that have gone on to have a high impact,” says Kate Clancy from the University of Illinois. “I wonder if that's because I publish mostly with women. My few publications that have a few male authors were far easier to publish.”

Holman and his colleagues argue that journals could address these problems by hiring more women editors, inviting more women reviewers, and implementing double-blind policies, where neither the editors who handle papers nor the reviewers who judge them know the gender of the authors at first. “That seems like something we can fix now, and I challenge these big journals to change this,” says Ramirez. “If journal articles are the metric by which scientists are judged and promoted, then journals can really make a difference in all disciplines by changing their numbers. What goals have been set? Let’s see changes in the next one to five years, not 10 to 20.”

Many scientists have discussed other ways of reducing gender disparities, and Holman and his colleagues have ended their own paper with a “densely referenced and very long sentence that’s our take on the greatest hits.” Here it is, in full:

We suggest that efforts to recruit and retain women in STEMM [science, technology, engineering, mathematics, and medicine] must be wide-ranging and could include dispelling the common but poorly evidenced belief that there are innate gender differences in STEMM aptitude; reforming academic publishing and peer review; ensuring women have equal access to informal professional networks; affording greater recognition of the extra demands outside the workplace that traditionally fall on women when assessing candidates’ achievements; guaranteeing women equal resources at work; providing better access to parental leave and additional provisions to help people return to work following a career break; striving for a representative gender ratio of invited speakers at academic conferences; and affirmative action during hiring.

The team has also made their data freely available, and created an online app for exploring it. “I’m not an expert [on gender disparities],” says Holman “so I thought it was even more important than usual to make the data accessible. It’s a slightly shaky website but my hope is that people from the social sciences take this up.”