Earlier this week, I came across a Nature News article highlighting the gender-based pay gap in STEM fields. (Nature and Scientific American are both part of Springer Nature). It turns out that, one year after completing their studies, female PhD graduates in the U.S. earn almost one-third less than their male counterparts. The difference can be attributed to just two key factors, according to a study published in American Economic Review

The first factor is that women tend to go into comparatively less lucrative fields—biology or chemistry, for example, as opposed to math or engineering. While this fact undoubtedly deserves further scrutiny in terms of why this is the case, it’s still somewhat easy to brush aside. After all, women are making these decisions of their own volition, presumably knowing that their field of choice has relatively low earning potential among STEM professions.

However, the second factor is a bit more troubling…if depressingly predictable. Even when the field of academic study is removed from the equation, women’s earnings still trail those of men by 11 percent. The reason? Family. Married women with children are paid less than those who don’t have similarly structured families. Meanwhile, men earn the same amount, regardless of their marital or parental status. 

This is unsurprising to me, not only because it has been widely studied and reported in the past (not just in STEM fields, of course, but across the spectrum of professions), but also because I have seen it firsthand. As a woman who has worked in overwhelmingly female-dominated fields in the past, I have been struck by two recurring observations: (1) Even though a significant majority of individuals in my field were female, the most senior (and thus presumably highest paid) positions were disproportionately occupied by men; and (2) Those women who did hold such leadership positions were often unmarried and almost invariably childless, while their male counterparts were nearly always married with children.

But I digress. Anecdotal evidence aside, the data are what really tell the story. While the Nature story did not include a data visualization, I subsequently happened upon a related story from The Wall Street Journal, featuring a handy interactive graphic. Drawing data from the Census Bureau, this information-rich visualization represents 446 major U.S. occupations, from the lowest- to highest-paid. Using a lollipop-style chart, the graphic highlights the gaps between male and female earners, with men almost exclusively boasting comparatively higher wages.

Graphic from The Wall Street Journal. Interactive visualization by Lam Thuy Vo and Jessia Ma; additional development by Andrew Van Dam and Stuart A. Thompson.
Click the image above to launch the interactive.

The largest pay gaps are easy to identify, as the lines stretching between male and female data points stick out like proverbial tall poppies next to their more modest neighbors. Moreover, the gaps expand progressively towards the right-hand side of the graph, where more lucrative professions (i.e. those employing more highly educated individuals) are displayed.

Finance-related jobs apparently have some of the largest pay gaps.

As I scrolled across the visualization, I kept an eye out for STEM jobs likely held by PhD-educated individuals. It wasn’t hard to single many of them out, as several featured remarkably large pay gaps. Physicians and surgeons, for example, occupy the last position on the graph, boasting the highest wages overall; however, women in these professions make a mere 64 percent of what their male peers earn. 

Physicians and surgeons earn the highest wages overall, but also have one of the largest pay gaps.

Admittedly, grouping all physicians and surgeons into one broad category is not the best way to approach the pay gap question, as surgeons are generally paid significantly more than, say, family doctors. However, considering the sizeable pay gaps in other medical fields, such as podiatrists (65 percent), dentists (76 percent), optometrists (82 percent), and veterinarians (81 percent), it seems that some sort of institutional bias is likely a factor in the physicians/surgeons group. Other STEM professions with considerable pay gaps include natural sciences managers (74 percent), atmospheric and space scientists (84 percent), and astronomers/physicists (85 percent). 

While this visualization is quite informative and user-friendly, it also raises a number of questions and ultimately makes me wish for a new, more comprehensive and granular representation of pay gap data. For example, I’d like to see certain categories (such as physicians/surgeons) broken out into more specific occupations in order measure the pay gap more accurately. I would also be curious to see the ratio of male to female workers in each profession and evaluate any possible correlation between higher numbers of women in a given field and smaller pay gaps. And finally, I’d like some graphical indication of what factors influence the variations among these numbers. For example, what makes some fields (like biomedical engineering, where men and women actually earn equivalent salaries!) friendlier to women than others? 

In any case, it is clear that female professionals are disproportionately hindered by family-related factors, and this needs to be addressed on a number of levels. The intersection of different types of gender gaps also seems to merit further study, as one gap may easily beget others. 

For more on gender gaps in the sciences, check out this Scientific American interactive graphic from 2014.