Leaks in the Pipeline: When women leave science (Proceedings of the Royal Society B)

Young women outnumber  men in most university science classes, yet the number of tenured female professors remains far below that of men. The potential causes — discrimination, biological differences, personal preferences, societal pressures, or simply the time-lags associated with long careers — have been hotly debated.

In a paper published in the Proceedings of the Royal Society B, Princeton researchers modeled academic careers to disentangle time lags from gender-based differences. Although the research does not reveal exactly why women leave science, the study does indicate when they do so.

The investigators found that the slow progression of the typical science career – with years spent in undergraduate and graduate education, postdoctoral research, and untenured professorships — accounts for much of the current underrepresentation of women.

In other words, demographic inertia – the fact that it takes both women and men many years to get to the top of the scientific career ladder – plays a large role in the lack of tenured female professors in science.

The researchers used data collected over the past three decades by the United States National Science Foundation to compare a simulated “gender-difference free” situation to the actual numbers.

The model results demonstrated that the time lags in academic careers are indeed an important factor limiting the number of female faculty, and that it is unfair to expect a 50-50 ratio at present.

However, once this time lag was factored in, there were still considerably fewer female scientists than would be expected if there were no gender differences.  The pattern held for all scientific disciplines considered, although the extent varied by discipline.

Researchers found that in most disciplines, the biggest loss of women came between their PhD and faculty positions.

In a handful of disciplines, however, the lack of females in senior positions stems from the fact that very few women enter the field as undergraduates in the first place. These fields include mathematics, computer sciences, physics, and engineering. Those that do are more likely to continue to graduate school than their male peers.

Although the model could not pinpoint specific causes for the observed gender differences, the researchers noted that the fact that these differences are still shrinking. As these differences seem to be absent at selective career transitions (such as the granting of tenure), the researchers suggest that innate gender differences are not likely to be responsible for the lack of women in senior faculty positions.

The work was conducted by Allison Shaw and Daniel Stanton. Shaw is a graduate student in the laboratory of Simon Levin, the Moffett Professor of Biology in the Department of Ecology and Evolution, and Iain Couzin, assistant professor in Ecology and Evolutionary Biology at Princeton University. Daniel Stanton earned his Ph.D. in the laboratories of Henry Horn, emeritus professor, and Lars Hedin, professor of Ecology and Evolutionary Biology at Princeton University. Stanton is now a postdoctoral researcher at Australian National University.

Shaw, AK and Stanton, DE. Leaks in the pipeline: separating demographic inertia from ongoing gender differences in academia. Proc. R. Soc. B. Published online before print June 20, 2012, doi: 10.1098/rspb.2012.0822