Summary

The article explores the career trajectories and research practices of faculty members in U.S. higher education institutions, particularly focusing on transitions between Historically Black Colleges and Universities (HBCUs) and Predominantly White Institutions (PWIs). It utilizes data from the Academic Analytics Research Center (AARC) and Scopus to track faculty movement and publication records from 2011 to 2020. The study compares mobility patterns, research productivity, and collaboration rates, revealing disparities and impacts on research outcomes. The research provides valuable insights into academic mobility, disparities in research support, and the need to strengthen HBCUs to promote diversity, equity, and inclusion in US academia. The article is well written and relevant. Please find below some comments that I think could strengthen the results.

Comments:

• HBCUs are unique to the US context. I would suggest the authors to contextualize their work in terms of a case study and explain how these results can be interpreted in a larger global lens. Does the segregated organization of higher education of the US offer an opportunity to study systemic discrimination at the institutional level?
• P. 10. I’m surprised by the fact that there are more PWI-HBCU professors (79) than HBCU-PWI professors (60), which seems to go against the previous literature stating a brain drain. I do not follow why the authors do not highlight this first finding. In the conclusions, the authors say: “By tracking the mobility of 139 professors, our analysis suggests that the out-flow of HBCU faculty (79 professors) is larger than its in-flow (60 professors).” But it seems to be the opposite.
• Also, the PWI-HBCU professors go downward in prestige, which is in line with the previous literature on the downstream hierarchy of US faculty hiring (https://www.science.org/doi/10.1126/sciadv.1400005), but HBCU-PWI professors have the opposite tendency, which is highlighted by the authors, but not contrasted with the previous literature.
• Why only comparing PWI-HBCU, HBCU-PWI? The group PWI-PWI would work as a baseline for mobile authors not affiliated with HBCU, while the HBCU-HBCU group would be a very interesting case. Is the sample size a problem? Comparing with both non-mobile and PWI-PWI authors would allow to disentangle the mobility effect per se with the effect of the directionality.
• Why excluding self-citations? I don’t follow the motivation for this decision.
• P. 18. On the productivity changes. Given that PWI-HBCU and HBCU-PWI show very different trends in terms of upward and downward mobility, it is possible that the observed changes in productivity are due to this effect. This is to say, the penalty of moving to an HBCU can be the penalty of any professor that moves downward the ranking, regardless the mission of the institution (and vice-versa for HBCU-PWI). I don’t think this invalidates the point of the paper, but it does change the interpretation of results. The authors could create a control group with similar ranking changes for comparison.
• Why there are no confidence intervals for figure 3b? And also why the Figure 4 is based on the proportion of top publications then the authors could use as a dependent variable the normalized citations and JIF?
• On the collaboration results. Isn’t there a sort of artifact where the author’s affiliation defines the existence of a collaboration and when they change their own affiliation they also change the collaboration profile of their papers? For example, if an HBCU author always collaborate whit a PWI and then move to a PWI they would show a change from 100% to 0% in HBCU-PWI collaborations. The opposite would happen with a PWI professor that always collaborate with HBCUs. Nevertheless, given the smaller number of HBCUs, it is likely that when a HBCU affiliation is gained, the cross-type collaborations increase, but if it is loss, they decrease. For example, if a PWI professor collaborates with 2 ppl, one from HBCU and one from another PWI, and they change their affiliation to an HBCU, then the HBCU-PWI collaboration sustains. I hope I was clear enough.