Why female STEM PhDs are less likely to become new inventors

In the innovation economy, individuals with PhDs in STEM fields — such as engineering, chemistry, and biology — are increasingly being employed outside academia, where they contribute to commercial science through patenting.

But research from MIT Sloan shows that there’s a gender gap in access to faculty advisors who are prolific inventors — a key factor that influences whether students become early inventors themselves. A paper co-authored by MIT Sloan professor Fiona Murray and Copenhagen Business School’s Mercedes Delgado found that female STEM PhD students were 21% less likely than their male counterparts to have been trained by top inventor advisors — those who had received at least seven patents while employed by a university during the study’s time frame.

These advisors are important because they increase a PhD student’s chances of filing their first patent during their doctoral program (or soon after graduating) through a co-patent with that faculty advisor. According to the research, 4% of all STEM PhDs became new inventors, but when they were advised by a top inventor faculty member, their chances of becoming new inventors increased to 23%.

The issue is a complex one, the researchers note, with multiple factors determining how many women become inventors. Even when female STEM PhDs were matched with top inventor faculty members, they were 17% less likely to become new inventors during their time as PhDs (and in the two years afterward) compared with their male STEM PhD student counterparts.

“This means there is a ‘leaky pipeline’ of female inventors-to-be, even when these women make it into the labs of top inventor advisors at top universities,” said Murray, associate dean for innovation.

“Not surprisingly,” she said, “these findings have significant implications for inclusive innovation in STEM fields and more widely for the startups and large corporations who hire these talented students.”

Delgado and Murray’s research included about 185,000 PhDs who graduated from 1995 to 2015 from the 25 U.S. universities with the highest patent counts. While the number of STEM PhD graduates had a 4% annual growth rate, the number of new inventor PhDs increased by 7% annually. That means that “over time, universities are increasing the engagement of PhD students in patenting,” the authors write.

Of the top inventor advisors included in the study, only 8% were female (68 versus 808). The authors found that female PhDs were more likely to be trained by female rather than male top inventors. However, once they controlled for the pool of PhD advisees by gender for each top inventor advisor, the rate at which PhD students became new inventors was lower for women compared with the rate for men by at least 4 percentage points, regardless of the gender of the advisor.

Early intervention and encouragement can help

There’s no single fix for the gendered imbalance among new inventors, but Delgado and Murray offered several actions for consideration to increase the number of women among new-inventor PhD students.

One suggestion is to increase the number of female PhDs who are trained by top inventor faculty advisors, though the researchers write that this would also require a better understanding of the advisor-advisee matching process. At the least, according to Delgado and Murray, incoming PhDs should understand the significance of their advisor choices.

Universities could also encourage female faculty members themselves to engage in higher levels of patenting. According to the paper, on average, female top inventor advisors have a higher female share of PhD advisees than male top inventor advisors do, even when controlling for thesis topic.

“An indirect outcome of programs to encourage female faculty to engage in high levels of patenting will be more female new inventor PhDs,” the researchers write.

And to address the leaky pipeline of STEM female PhD inventors-to-be who have already been matched into the labs of top inventor advisors, the authors recommend actively encouraging those students to participate more in patenting. But Delgado and Murray write that the factors shaping patenting once students are in the lab are “poorly understood” and there is more to be learned on the supply and the demand sides.

Supply-side factors to be considered include differences between female and male advisees in patenting preferences, self-assessments of invention skills, and access to resources such as university technology transfer offices. On the demand side, “our findings are consistent with the idea that women’s innovation skills and contributions are somewhat undervalued by advisors,” Murray said. “Even in the same lab with the same advisor and in similar fields, female PhDs have a lower probability of patenting.”

Early training in patenting and commercial science is particularly important for students entering their commercial careers, but it also impacts the broader U.S. economy.

“By offering more opportunity and access to further training and experience with the patenting process and other entrepreneurial activities for all PhD students — but especially for women — we will improve innovation throughout the economy at a time when this is especially important for national and global competitiveness,” Murray said.