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The Leaky Pipeline for Women in Physics and Astronomy

by Fran Bagenal

Fran Bagenal is Professor of Astrophysical and Planetary Sciences at the University of Colorado.
She studies magnetic fields and plasmas surrounding planets. While she encourages women scientists
to learn to say “no” to more tasks, she admits she was co-opted by Meg Urry to be program chair
of Women In Astronomy II and to edit STATUS.

June 2004


The science career pipeline is being hotly debated. Is it preferentially leaky for
women? Is it an outdated metaphor for a complicated issue? At the Women In Astronomy
II (WIA II) conference held at Caltech in June 2003, recent data on faculty numbers in physics
and astronomy indicated the leaky pipeline to be fixed. I was prompted to roll up my sleeves and
dig down into the data. I found there is indeed encouraging news for some women at the faculty
section of the pipeline. But locally there remain enormous variations among institutions and
overall very serious differential leaks persist for women at college levels. Moreover, the overall
input to the pipeline, the total numbers of undergraduate degrees in physics, is limiting growth of
the field. The latest AAS membership data reveals a cohort of young astronomers comprising a
startling high 60% of women, providing an opportunity to study a group as they move
through the pipeline and ask these women what factors shape their career paths.

The Numbers: Pipelines and Scissors

The first time I recall seeing “the pipeline” used to refer to the flow of people along careers
in science was in Sheila Widnall’s AAAS presidential address “Voices from the Pipeline” (Widnall 1988,
see excerpt in this issue). Her address began with the frequently-repeated policy refrain that the
nation is in dire straits and that we need to train more people in science and engineering:

“Demographic trends predict a future significant drop in the numbers of white males of college
age, who have been the dominant participants in science and engineering. The likely effects of
these trends on scientific and engineering personnel have been documented by the NSF and OTA of
the US Congress. If current participation rates continue, the future pool of science and
engineering baccalaureates is projected to show a significant drop. We have now passed the peak of
US graduate students available from traditional pools and are headed down the slope to a 26%
decrease in the pool by the late 1990s.”

In reality, the number of degrees in science and engineering, did not drop precipitously (they increased
through the 80s and 90s, partly due to an increasing participation of foreign students), but a recent National
Science Board report on the science and engineering workforce repeats the refrain (NSB 2003). As I
shall discuss below, the numbers for the physics profession remain worrisome.

For Widnall the demographic trends were the entree for a discussion of women in science. Based on
a 1985 OTA report she presented a grim picture:

“Of an initial cohort of 2000 male and 2000 female students at the ninth grade level only 1000
of each group will have sufficient mathematics capabilities to remain in the science pipeline.
When the two groups are followed to the end of high school, 280 men and 220 women will have
completed sufficient mathematics to pursue a technical career. A major drop in women students occurs with
career choice upon entering college, with 140 men and 44 women choosing scientific careers.”

She presented a dramatic diagram (Figure 1a) that shows this continued steep decline in numbers
through graduate school. “Of the original 2000 students in each group, five men and one woman
will receive the PhD degree in some field of natural science or engineering.” I show another
version of this leaky pipeline diagram in Figure 1b.

In her paper Widnall concluded from the steeper slopes in Figure 1a that the most fruitful
areas to concentrate on would be the initial career choice (entering college) and graduate
school years. The remainder of her presidential address is a very interesting summary of surveys
of graduate students at Stanford and MIT. Her findings are not likely to surprise a reader of
STATUS (issues of self-esteem, aggressive styles of communication and occasional egregiously bad
behavior) and it is impressive that she used her presidential address to highlight the issues.

Moving forward 15 years to 2003, how has the leaky pipeline changed? From here onwards I
shall limit my discussion to physics and astronomy rather than address the whole of science and
engineering (for which the National Science Board has a 2003 workforce report, NSB 2003).
The statistics division of the American Institute of Physics has been gathering data for many years
for the physical science profession. At WIA II Rachel Ivie presented recent AIP studies of
women in physics and in astronomy (Ivie and Nies 2003). Their version of the pipeline issue is
presented as the “scissors diagram” in Figure 2. Rather then show absolute numbers (as in Figure
1), these scissors plots show the percentage of women at each stage. Thus scissors plots show
the differential leak of women along the pipeline.

Figure 2 shows a huge leak between high school and PhD. The net drop from high school
to college is a little less steep for astronomy, a little worse for physics than that shown for all of science
and engineering in Figure 1. The post-PhD story for physics and for astronomy is more encouraging,
the actual percentage follows that predicted from earlier production of bachelor degrees, and
slightly better in the case of astronomy. This suggests that all we need to do is wait for the
increasing supply of women to come through the pipeline and the scissors will slowly close up.
Now the word is spreading that the leaks in the pipeline are all fixed.

This inference that everything is hunky-dory did not sit well with many of us women
astronomers who are actually (swimming?) in the flow. It just does not to reflect our own experiences.
To further examine the issue, I took Rachel Ivie’s data and the 2003 astronomy data compiled by the CSWA (Hoffman and Kwitter 2003) to produce Figure 3.

Graduate School Leaks

In her WIA II presentation Ivie showed the percentage of degrees in physics and in astronomy
awarded to women from 1966 to 2001 for bachelor and PhD degrees (top panel of Figure 3, based on
Ivie and Nies 2003). Each profile shows a roughly factor of four increase in the percentage of
women getting degrees over the past 30 years. The percentages are nearly a factor of two higher
for astronomy than physics, but also more erratic due to much smaller (factor of 10-20) absolute
numbers. Estimating that the average time between degrees to be six years, I then translated
the bachelor profiles to the right by six years. Sure, only a fraction of those getting bachelors
degrees go on to complete a PhD, but if the pipeline were not differentially leaky for women,
the translated curves should line up with the PhD curves. For physics there is clearly a substantial
difference between the current actual percentage of ~13% and the expected value of 17-18%. For
astronomy the erratic nature of the curves muddies the story, but for the past 7 years the award of
PhDs to women has been persistently below expectations based on the percentages of women
with bachelor’s degrees (e.g., in 2001 the expectations based on bachelor’s degree production 6 years
earlier would be that 30% of PhDs would go to women when the actual numbers are only 3/4 of
these expectations with 22% of PhDs going to women). One might imagine that women who
have children during graduate school might take a little longer to get a PhD but the average time
to PhD would have to be many additional years to make the curves overlap. Thus, the differential
leak in the graduate school section of the pipeline remains substantial, the underlying causes of
which our profession should investigate. Discussions at WIA II confirm that the poor work
environment reported by Widnall (1988) still apply to physics and astronomy programs across
the nation.

Faculty Leak Stemmed?

To investigate leaks further along the pipeline I took the PhD time curves and translated them
according to the average number of years since PhD for the three main faculty ranks (shown in
Table 1). The increase in hiring of women is reflected in the smaller mean number of years
since PhD for all ranks. To calculate the expected percentages of women in these three ranks for
physics and for astronomy I translated the PhD curves by the full range (mean for women to
mean for men), shown by the broad, paler curves in Figure 3. The black curves are the expectations
based on the mean years for women. For comparison, the actual percentages of women in
these ranks are shown by stars, based on data from AIP and from the 2003 CSWP survey of astronomy.

Figure 3 shows that for assistant professors in physics over the past decade the percentage of
women has been above expectations. In astronomy the percentages of women assistant professors
quoted by the AIP and CSWA straddle the curve. For associate professors the physics record
remains just above expectations while for astronomy the percentage of associate professors (23-25%)
seems to soar above the “pipeline values” of 10- 15%. Extrapolations over the 20-30 years
between PhD and full professor are somewhat risky but the actual values for the full professors fall below but comparable to expectations. Thus, indeed, when one looks at national statistics the
faculty section of the pipeline does not seem to be differentially leaky for women. We eagerly await
the impact over the next decade of the high fractions of women at assistant and associate levels for
physics and astronomy on both the statistics for full professors and on numbers of women students.

No Time for Complacency

While the percentages of women in faculty positions are indeed quite encouraging, there are
several reasons to remain cautious before the community pats itself on the back and dismisses
the leaky pipeline as history. For example, when one looks at the results of the 2003 CSWA survey
of astronomy faculty one finds huge variations among institutions. Several astronomy departments
have extremely few or no women faculty at all. Table 2 compares two universities with large,
strong astronomy departments – Columbia and Cornell – that illustrate this wide range in
representation of women. Departments such as Boston University where the number of women
faculty increased from zero in 1992 to 5 out of 24 in 2003 show that change is possible. Millie
Dresselhaus (AAAS president who reviewed of the status of women at many physics departments)
noted that sometimes it only takes one faculty member - male or female – making an effort to
affect substantial change. Yet, even when someone on a search committee makes an effort to consider
women candidates they are faced with tendencies for lower application rates among women and
higher probability of a “2-body problem” (Figure 4). Nevertheless, the CSWA survey demonstrates
that many departments have surmounted these obstacles. Denice Denton, Dean of Engineering at
University of Washington, presented at WIA II a host of ways to increase the hiring of women
(Denton 2003). A useful vehicle for change can be an external review by a group such as the APS
Committee on the Status of Women in Physics which offers to visit a department and provide advice.

Finally, in her presentation at WIA II Margaret Kivelson (UCLA) cautions that in her
experience of academia since the 60s there can be regressions. Pointing out that after a steady rise in
the 70s and 80s, the current (total) faculty hires at UCLA show a sharp decreasing trend in the
percentage of women, she warns, “It takes effort even to keep from losing ground.”

Broken Metaphor?

The faculty path is only one branch of the pipeline after PhD. The are many other career
paths of successful, productive physicists and astronomers at research labs, in industry, as
journalists, etc. While it is important that those institutions who train future generations of scientists
include a substantial fraction of women, it is just as important that we do not lose valuable assets,
often trained at significant expense, through leaks in the pipeline elsewhere in the system. In fact, it
may just be that the fraction of women is much higher in these “alternative” career paths. Sadly, it
seems that attention is paid almost exclusively to statistics of the academic track. We urgently need
similar studies of demographics of all post-PhD branches of the pipeline.

Some people argue that the whole concept of a pipeline is inappropriate. It implies scientists
are passive particles carried along by a flow over which they have no control. In a recent book
Women in Science: Career Processes and Outcomes (reviewed by Rosser 2003), sociologists
Yu Xie and Kimberlee Shauman argue that the pipeline metaphor is not appropriate because no
simple theory explains the dearth of women in science and no one policy will provide a simple
solution. Furthermore, they claim that the pipeline metaphor implies a single means of entry
and does not allow for women entering science and engineering at different stages. In a similar
vein, the common tendency for discussions to revolve around “the perfect trajectory” from
school through college to a faculty position was strongly criticized at WIA II.

Personally, I do not believe women scientists think of themselves as passive particles and, naturally,
we should encourage women to take active control of their destiny. While I accept that we need to
examine – and celebrate - the multiple professional branches of our field, I argue that the pipeline
metaphor remains a very valuable one. It is naïve to believe that one can enter a career in physics or
astronomy except via a substantial number of years along what is undeniably a fairly uniform,
standard pathway of college education in math and physics. This is a reality of a rigorous scientific
profession and cannot be changed because sociologists believe people should be entitled to pick and
chose a random path through life. The fact that many, many women have found satisfying careers
in science does not mean, however, that the pipeline couldn’t do with some improvements
(e.g. with a healthier work environment, ways to handle 2-body problems, accommodation for
families, etc). It has been obvious all along that there is no single “silver plug” that will stem the
leak of women from scientific professions. Yet, the metaphor has been useful for drawing attention
to the problem (and proposing solutions) with our colleagues, with administrators and with funding
agencies. The pipeline has branches, is leaky in places and we need to find better ways to accommodate
having a family along the way - but it isn’t broken!

Watch the Inflow

While the pipeline branches after the PhD, the input to the conduit is largely restricted to those with undergraduate degrees in physics or astronomy (plus a few from mathematics). To a large extent, therefore, the input to the pipeline is critically dependent on the numbers of physics and astronomy degrees.

Figure 5 shows that the total numbers of degrees (both bachelor and PhD) for physics is
static (one might even say oscillatory with a 20- year period). There is a glimmer of hope that the
number of physics bachelor’s is at last swinging upward, helped by the slow increase in women
attaining physics degrees. For astronomy the trends are more positive but the numbers are much smaller.

Over the past few years there have been several investigations of causes of the low graduation
rates in the sciences and physics in particular (e.g., Tobias 1994, Seymour and Hewitt 1997).
They conclude that many of the aspects of physics undergraduate education that lead to students
dropping physics are opinions generally shared by those who persist – the “stickers.” The stickers
just put up with what is all too often poor instruction and less than welcoming attitudes. The attitude of
many physics faculty and TAs, that only the very brightest, toughest, nerdliest can stay the course,
is stifling the field. At the same time, there are some shining examples of faculty and departments
where the physics teaching is improving by leaps and bounds (e.g., see Tobias 1992, NRC 1999,
McCray et al. 2003). Recent issues of Physics Teacher or the American Journal of Physics show
examples. The AAPT has week-long conferences and AAS meetings have sessions on education.
Yet, there are still departments, many at the better universities, where the teaching methods have
barely changed since the turn of the century – the 19th century. The one factor that could most
radically improve the pipeline – in terms of both absolute numbers and to fix the differential leak
of women – is to improve the quality of experience for undergraduate students taking physics courses.
This is something over which those of us who are faculty in physics and astronomy have some control
and we need to act.

At the same time, improving the undergraduate experience is not just for faculty. There are several
things that those earlier in the pipeline can do to help those following behind them. One issue that
concerned me when I was on the graduate admissions committee in my department was that many of
the applicants had little idea about applying to graduate school. The GRE scores in physics were
highly erratic and poorly correlated with GPA in physics courses. Few letters from the students
conveyed the information we were looking for and many students picked faculty who barely
knew them (or had no idea what to say) to write references. This is not necessarily the student’s
fault. How is a brilliant student at Podunk College supposed to know these things? Or, for
that matter, how are students at Stanford and MIT supposed to learn that the name on their
undergraduate degree means diddly-squat when they have Cs in physics or their physics GRE
score is in the 4th percentile? These are things best learned from graduate students and postdocs
who make the effort to mentor their local undergraduates or the laboratory researcher who
talks to the summer interns about their careers. For that matter, think of the potential impact of
each undergraduate who gets fired up by a research project visiting a couple of local high
school physics classes.

Improving the undergraduate experience is key to the livelihood of our profession. But it
takes more than a change in administrative policy to improve the quality of the work environment.
Indeed, to quote Meg Urry’s report on WIA II in the AAS newsletter “some undergraduate women
report troubling, hostile environments, at the hands of their young male colleagues - notably, it
isn't a story of older, traditional astronomers who just can't change, it's a new generation of arrogant
and overly-entitled young men who apparently can't credit young women with intelligence,
dedication, or a future in astronomy.” None of us can afford to condone such behavior. Whether as
a director of a lab or as “just another particle in the flow” we all need to speak out.
One of the most inspiring moments of the WIA II conference was the applause for the 2003
AAS statistics. Kevin Marvel, Deputy Executive Officer of the AAS, presented the membership
statistics showing women now comprise 60% of the 18- to 24-year-old membership (Figure 6).
Credit is suspected to be partly due to the enhanced support at NSF for the REU program
which supported research projects for undergraduates, many of which have been presented at recent AAS
meetings. This large group (75 under 23, 530 under 28) provides a great opportunity to follow
a cohort, including substantial number of young women, along the pipeline and to study what factors
influence their career choices.


1. There remains a significant differential leak of women in graduate school along the academic
pipelines for both physics and astronomy. The percentages of PhDs awarded to women in 2001
are 13% and 22% for physics and astronomy respectively while the expectations based on the
percentages of women obtaining bachelor degrees in these two fields are 18% and 30%
respectively. Until these leaks are stemmed, the flow of women into higher positions will be limited.

2. The statistics for faculty in physics and astronomy show that the percentages of women
in the three main professorial ranks approximately match expectations based on past PhD percentages.
There is encouragement in these national statistics where the actual percentage of women physics
assistant professors is higher than expectations and the percentage of women astronomy associate
professors is substantially higher. Past experience warns against complacency in the face of good
news, however, to avoid regression to a less favorable state. While the national news is
encouraging, the local statistics (as demonstrated by the CSWA survey of women faculty in astronomy)
show enormous variations across the country where several of the top university departments
still have very low percentages of women faculty.

3. We cannot expect a large increase in the flow into the pipeline in the near future. The
trend in the absolute number of graduates with bachelor’s degrees in physics is just starting to
increase after a decade of decline from 4300 (in 1986) to 3300 (in 1996). The small number of
astronomy degrees (~150 per year) has been slowly rising, mainly due to increasing numbers of women. These slow-growth trends are disturbing. Who will be the future astronomers to analyze
data from the new telescopes and missions planned for the next decade? Who will replace
the faculty retiring from the 60s hiring bulge? Improving high school and college physics education
remains a national imperative.

4. AAS membership data show the members between 18 to 24 years in 2003 comprise ~60%
women. The young members of the Society provide an opportunity to follow a cohort through the
astronomy pipeline, to document their career paths and why they chose them.

Acknowledgements: FB thanks Rachel Ivie and Kevin Marvel for data as well as Margy
Kivelson, Meg Urry, Stefanie Wachter and the CSWA for discussions on this issue.


Presentations at Women In Astronomy II - http://www.aas.org/~cswa/WIA2003.html
American Institute of Physics Statistical Division - http://www.aip.org/statistics/index.htm
Denise Denton’s Advance program - http://www.engr.washington.edu/advance/
CSWA Astronomy Survey 2003 - http://www.grammai.org/astrowomen/stats/
NRC Study of Undergraduate Education - http://www.nap.edu/catalog/10711.html
Committee on the Status of Women in Physics - http://www.aps.org/educ/cswp/index.html
CSWP Site Visits - http://www.aps.org/educ/cswp/visits/index.html
Sheila Widnall’s AAAS Presidential Address - http://web.mit.edu/aeroastro/www/people/widnall/aaas_pres.pdf



Denton, D., The Washington ADVANCE Program, Women In Astronomy II, Pasadena CA, 2003

Hoffman, J.L. and K.B. Kwitter, Results from the 2003 CSWA Survey of Astronomical Institutions, Women In Astronomy II, Pasadena CA, 2003

Ivie, R., and K. Nies, Women in Physics and Astronomy 2003, Women In Astronomy II, Pasadena CA, 2003

Ivie and Stowe, 1997-8 Academic Workforce Report, American Institute of Physics, 1998

Marvel, K., AAS Membership Demographics, Women In Astronomy II, Pasadena CA, 2003

McCray, R.A., R. L. DeHaan, and J.A. Schuck, (Eds), Improving Undergraduate Instruction in Science,
Technology, Engineering, and Mathematics: Report of a Workshop
, National Academy Press, 2003

National Research Council, Transforming Undergraduate Education in Science, Mathematics, Engineering and Technology, National Academy Press, 1999

National Science Board, The Science and Engineering Workforce: Realizing America’s Potential, National Science Foundation, 2003

Rosser, S. Review of Women in Science: Career processes and Outcomes by Y. Xie and K. Shauman, Science, 302, 1506- 7, 2003),

Seymour, E. and N.M. Hewitt, Talking of Leaving: Why Undergraduates Leave the Sciences, Westview Press, 1997

Tobias, S., They’re not Dumb, They’re Different: Stalking the Second Tier, Research Corp., Tucson AZ 1994

Tobias, S., Revitalizing Undergraduate Science: Why Some Things Work and Most Don’t, Research Corp., Tucson AZ 1992

Widnall, S.E., AAAS Presidental Lecture: Voices from the Pipeline, Science, 241, 1740-1745, 1988

Xie, Y., and K. Shauman, Women in Science: Career Processes and Outcomes, Harvard University Press, 2003

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