It's widely known that women are underrepresented in science, technology, engineering and math fields, but the idea that women leave the STEM pipeline after entering college at higher rates than men isn't necessarily true, according to a new study from Northwestern University.

The so-called "leaky pipeline" theory suggests factors such as discrimination and a lack of interest make it more likely that women will leave academic STEM fields. In other words, women who earn bachelor's degrees in STEM fields may be less likely than men to earn a doctorate in a STEM field.



But an analysis of 30-year trends in pSTEM fields – those in physical science, technology, engineering and mathematics – shows the gender gap in persistence rates actually has closed since the 1970s, when men were nearly two times as likely to later earn a relevant doctorate. By the 1990s, the gap had completely closed, the study found. Researchers David Miller of Northwestern and Jonathan Wai, a Duke University Talent Identification Program research scientist, chose to focus on pSTEM fields and exclude social sciences and life sciences.

"There’s been a lot of focus on this idea of women in particular leaving academic science at far higher rates than men," says Miller, an advanced doctoral student in psychology at Northwestern and lead author of the study. "But in some cases … there’s been scant evidence of some of those gender gaps in persistence, and evidence that those gaps in persistence don’t exist at other time points."



That's not to say, however, that women and men are equally represented in pSTEM academia. Men still outnumber women about 3 to 1, Miller says. But the differences are not explained by gender bias in the pipeline – the percentage of women earning pSTEM degrees is now higher at the doctoral level than at the bachelor's degree level, the researchers found.



"We need to start reframing the conversation from instead of just trying to plug leaks, we need to get more students interested in the first place," Miller says.



The percentage of women in pSTEM fields at the bachelor's degree level reached a peak of 28 percent in 2002, the study showed, before starting a decline. Women now make up 25 percent of all such bachelor's degree recipients. Recently, female representation at the doctoral level has begun following suit. After reaching a peak of 28 percent in 2009, the percentage of female pSTEM doctorate recipients has declined, now making up 27 percent of that population.

"It’s concerning because the gaps in persistence have already closed," Miller says. "Women would need to overtake men in terms of persistence rates in order to reverse that trend. Otherwise we’ll likely see a trend at the Ph.D. level to continue in the next few years and potentially change the impressive progress at the later levels."











"This idea of a leaky pipeline is inaccurate for nearly all postsecondary pathways in STEM," Miller says. "It fails to acknowledge many students who leave these fields might end up using their technical skills creatively in other fields like health, journalism or politics. It’s important to show STEM skills can also lead to non-STEM jobs. That's important for both men and women."



