The Possible Role of Resource Requirements and Academic Career-Choice Risk on Gender Differences in Publication Rate and Impact

Many studies demonstrate that there is still a significant gender bias, especially at higher career levels, in many areas including science, technology, engineering, and mathematics (STEM). We investigated field-dependent, gender-specific effects of the selective pressures individuals experience as they pursue a career in academia within seven STEM disciplines. We built a unique database that comprises 437,787 publications authored by 4,292 faculty members at top United States research universities. Our analyses reveal that gender differences in publication rate and impact are discipline-specific. Our results also support two hypotheses. First, the widely-reported lower publication rates of female faculty are correlated with the amount of research resources typically needed in the discipline considered, and thus may be explained by the lower level of institutional support historically received by females. Second, in disciplines where pursuing an academic position incurs greater career risk, female faculty tend to have a greater fraction of higher impact publications than males. Our findings have significant, field-specific, policy implications for achieving diversity at the faculty level within the STEM disciplines.Comment: 9 figures and 3 table

Career lengths of faculty members.

<p>Career length distribution of female (red) and male (blue) current faculty members for a selected set of U.S. universities (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone-0051332-t001" target="_blank">Table 1</a>). Data is binned into two year intervals. Currently, females hold about 16% of faculty positions in chemistry and in material science departments, and about 25% of faculty positions in molecular biology departments.</p

Higher publication impact of female faculty is correlated with higher relative risk of academic career choice.

<p>Risk in academic career choice and difference in publication impact. We quantify the risk of academic career choice according to Eq. (10). We show results for two alternative measures of difference in publication impact. In (<b>A</b>), we defined the gender difference in publication impact as the average <i>h</i>-index z-scores of females. The error bars indicate standard errors. See Fig. S13 for the statistical significance of the gender difference in publication impact. The trend line (black dashed line) indicates a significant positive correlation (coefficient of determination ). In (<b>B</b>), we defined the gender difference in publication impact as the probability that female authors have larger <i>h</i>-index z-scores than male authors, as depicted in Fig. S13. The trend line (black dashed line) indicates a significant positive correlation (coefficient of determination ). Note that the values of the risk of academic career choice in (<b>A</b>) and (<b>B</b>) are different for each discipline because the coefficients in the linear regression are different. The data suggest that in disciplines where it is risky to pursue an academic career, female faculty have publications with higher impact than male faculty.</p

The leaking pipeline.

<p>Percentage awarded to females of the total number of bachelor (green lines), master (blue lines) and doctoral (purple lines) degrees in the period 1966–2008. We obtained these data from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332-National1" target="_blank">[40]</a>. We also show the percentage of female faculty in our datasets (orange lines). We could not obtain separate data for molecular biology, so we show the data for biology instead. The grey shaded areas indicate values lower than 50%. The gender ratio of the faculty members given by our data is close to that reported elsewhere. For example, in our data, the percentage of female faculty members in chemistry is 16.2%, and according to the report of Chemical & Engineering News, this percentage is 17% <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332-Rovner1" target="_blank">[43]</a>.</p

Linear models predicting the gender difference in publication impact.

<p>The gender difference in publication impact is defined as the average <i>h</i>-index z-scores of females. , time to reach career independence. , reciprocal of salary premium of non-academic careers. , ratio of Ph.D. graduates pursuing an academic position. . The -values indicated below were obtained with the permutation test, but using Student’s t-test yields similar results.</p

Time to career independence.

<p>Fraction of publications in which a faculty member is the last author (purple diamonds) and the fraction of publications in which a faculty member is the first author (green squares). In many disciplines, the senior author of a study is listed last. Looking at the change in the fraction of times a faculty member in our dataset is a first or last author can thus be used as a proxy for change in seniority-level of an individual in these disciplines. We order publications, excluding single-author publications, by years after first publication and aggregate within each discipline. We fit the data to generalized logistic functions (green/purple lines) and define career independence (grey shaded areas) as the mid-point of the logistic function for fraction of last-author publications (Methods, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332.s015" target="_blank">Table S11</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332.s016" target="_blank">S12</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332.s017" target="_blank">S13</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332.s018" target="_blank">S14</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332.s019" target="_blank">S15</a>, S16, S17). While we do not observe gender effects (Figs. S11, S12), we do observe differences between fields.</p

Lower publication rates of female faculty is correlated with higher requirements for research resources.

<p>Effects of the magnitude of the resource requirements on the difference in publication rates between genders. Ecology is not included as we could not obtain data for resource requirements. The difference in publication rates is measured by the average z-score of number of publications by females in each year, and the error bars indicate the standard errors. The resource requirements is defined as the average annual research expenditure per principal investigator in the departments studied (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone-0051332-t002" target="_blank">Table 2</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051332#pone.0051332-National1" target="_blank">[40]</a>). The trend line (black dashed line) indicates a negative correlation (coefficient of determination ). These data suggest that higher resource requirements lead to greater differences in the publication rates between females and their male peers.</p

Comparison of publication impact for authors with different numbers of publications.

<p>The z-score of the -index as a function of number of publications. We use the mean and standard deviation obtained from the parameters in the model to determine the z-scores.</p