PCSY-D-25-00056

Research university assortativity conditions the integration of regional innovation systems

PLOS Complex Systems

Dear Dr. Petersen,

Thank you for submitting your manuscript to PLOS Complex Systems. After careful consideration, we feel that it has merit but does not fully meet PLOS Complex Systems's publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript within 60 days Oct 25 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at complexsystems@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pcsy/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

* A rebuttal letter that responds to each point raised by the editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. This file does not need to include responses to any formatting updates and technical items listed in the 'Journal Requirements' section below.

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If you would like to make changes to your financial disclosure, competing interests statement, or data availability statement, please make these updates within the submission form at the time of resubmission. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

We look forward to receiving your revised manuscript.

Kind regards,

Gaoxi Xiao, PhD

Academic Editor

PLOS Complex Systems

Gaoxi Xiao

Academic Editor

PLOS Complex Systems

Hocine Cherifi

Editor-in-Chief

PLOS Complex Systems

Journal Requirements:

If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise.

Additional Editor Comments (if provided):

Three Reviewers have reviewed the paper. While all Reviewers agreed that the paper may be of merits, some nontrivial concerns have been raised by the Reviewers, on whether the results are representative for research/education systems elsewhere, and some technical details of the analysis methods, etc. Authors are suggested to carefully consider these questions/comments, making responses to these comments and more importantly, necessary revision to their manuscript.

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Reviewers' Comments:

Reviewer's Responses to Questions

Comments to the Author

1. Does this manuscript meet PLOS Complex Systems’s publication criteria? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I don't know

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS Complex Systems does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I find the topic of this article quite interesting, as it explores potential patterns in academic collaboration between different universities. The analytical approach is largely feasible, and the conclusions drawn appear reasonable.

I would like to comment on the regression section. First, what is the rationale for selecting this specific form of the equation? Is there more foundational support for this choice? Additionally, does the model satisfy the necessary assumptions for regression analysis—such as a discussion of endogeneity issues, among others?

Reviewer #2: As I understand it, the paper uses data on multi-campus universities---UC and UT in particular---to understand regional innovation systems. It highlights variation in institutional homophily and sorting, and it argues for a mediating role for the research profile of a university in addition to a moderating role for institutional homophily. The analysis draws on Web of Science data and focused attention on the economic shock of the financial crisis in the late 2000s.

I appreciate the overall intuition behind the paper, that multi-campus universities play an important but underspecified role in regional innovation systems. I also enjoyed reading the fairly sophisticated analysis. There is a story worth telling in this paper.

But there are some analytical decisions and some aspects of the writing that I find a little concerning. These are numbered below to make them easier to follow.

1. Databases like Web of Science suffer from a lot of missing affiliation data prior to 2008. Given that the paper is structured around an economic shock that happens around the same time, I would want to see some work that shows the changes they observe are not just database artefacts. One of the ancillary claims in the paper (around RQ4) is that the system exhibits some resilience by "bouncing back" after the shock. The argument is weakened a lot if that is only the residue of a data production process in the database itself.

2. Presumably, many of the papers that get counted come from people with multiple affiliations. Does that count as co-creation in the same sense as a collaboration across two institutions? If so, why? Are the findings robust if these papers are excluded?

3. The text of the article says that the research here is about regional innovation systems, but the analysis itself is about the much narrower topic about multiple campus universities and their co-production of scientific research. The paper would be made much stronger if there was a clearer explanation of where the actually-analyzed phenomenon fits into the larger topic of regional innovation systems. As it stands, the results seem a bit overstated because of the lack of an explanation.

4. Relatedly, the paper would benefit from a more clear statement about the universe of cases that were NOT analyzed. The UC and UT systems are powerful scientific centers, to be sure. But once we move beyond the analysis here, what other cases could we plausibly think about generalizing to? Does the University of Paris or the University of London count? The individual brands there may be stronger than the larger UP or UL brands. What about other university consortiums like those in China? What about other traditional multi-sited universities like the University of Toronto? What about NYU + NYU Abu Dhabi? Or are we *only* taking about UC and UT? It would be helpful if the authors could clarify what the universe of cases are here, and if that universe is unclear or vaguely defined, how a reader should approach their study. What things should we expect to extend to which cases, and for what reasons?

5. It may not be practical, given the authors' justification of the case selection, but it would be very helpful to see a comparison to some kind of RIS/university counterfactual where there is no multi-campus university in the same sense, or where there is a multi-campus university of a different sort. For instance, I would be pretty surprised if CUNY and SUNY campuses contributed to the NY state innovation system in the same way that UC and UT do. My prior would be that Columbia and NYU do a lot of the heavy lifting there, and it would be interesting to see how that compares.

6. The writing could be organized in a clearer way. It is not easy to parse out the relevant information about each research question. Take RQ4. Is it ever fully addressed? I can see the relevance of various plots, captions, and stray sentences. But there is no clear statement of how the evidence addresses the RQ. There are similar but less extreme problems for following the evidence around RQ1-3.

7. I would have assumed, before reading the paper, that there should naturally be more co-production within the same field, as compared to interdisciplinary co-production. So it doesn’t surprise me that alignment is linked to co-production—that is a product of the researchers employed at each university. It may still be true that alignment increases co-production across disciplines compared to what it would have been with less alignment, but I don’t think we can conclude that on the basis of the evidence provided here. This is more of a musing now, than a well-formed comment, but do the results hold within specific fields? Do the engineers at CalTech co-produce more within-field research on the one hand, and more across-field research with a university that is closely aligned with its own research profile in comparison to universities that are less closely aligned?

Overall, I enjoyed reading the paper and I look forward to seeing it in print, whether it is published here or elsewhere. I do think it needs a little bit of work to smooth out the rougher edges, though.

Reviewer #3: This is a substantial attempt at defining the role of academic collaboration to regional innovation. The article is well written, and the topic is relevant to innovation policy and the support of collaboration practice. The analysis is thorough and the data well presented.

I provide a list of questions and points of reflection that could help the authors improve the manuscript:

1. The Jackard coefficient provides a simple ratio and could not capture the depth of collaboration, as would be indicated through patents or the length of that collaboration or knowledge production beyond academic publications. The measure is dyadic and cannot account for multilateral collaborations among multiple institutions. It therefore reduces the complexity that the authors intent to capture to a one dimensional coefficient. The authors would need to explain how this is an adequate method to capture the complexity of systems of systems.

2A. The method biases towards large institutions. Weighting by number of academic staff or research income (etc) would be advised.

2B. Publication data from 28 institutions appears to grossly underestimates the production of knowledge in a geography where the largest global corporations have concentrated proprietary research. The effects of this knowledge production to University research should be controlled for (e.g. through the research budgets of private actors) or recognised as confound to the models employed.

3. Bias towards disciplines with a tradition of multi-authored publications. These are not necessarily the disciplines that produce regional innovation this work attempts to capture.

4A. Choice of geography, would require further elaboration beyond some generic statistics. Texas and California are not necessarily representative of other global regions with high innovation potential.

4B. As the volume of academic production, patents and innovation shifts to SE Asia it would also be useful to know how (and whether) the patterns of collaboration observed are providing a means to "defend" the innovation advantage in the regions examined.

5. The methods employed do not adequately capture multi-lateral collaboration. Particularly when this involves regions beyond the ones studied.

6. Temporal dynamics are masked by the aggregation enforced by the use of Jackard.

7. There have been sophisticated models on networks of collaboration such as the triple-helix (Wagner and Leydersdorff, 2005) that capture the role of industry and government in conjunction to academic research.

8. The role of government and industry funding would need to be controlled for. As there is no baseline MUS in other parts of the country, this is difficult to implement.

9. The distinction between what is called mono-university versus MUS universities is premised on the assumption that all multi-University federations are equivalent. This appears to this reviewer to be an unrealistic assumption.

10. How would policy recommendations suggested address inherent negative side-effects of economic agglomeration? Innovation bottlenecks are well documented where innovation activity is concentrated.

11. The context of the financial crisis is not well theorised in the present context. While it had substantial impact in the availability of finance, particularly for start-ups, its effect on research finance was muted and delayed by the research awards cycle. On the other hand from 2012 to 2022 there has been a resurgence of venture capital, supported by negative real interest rates. This has made a major difference in the availability of finance for innovation, from which California and Texas have greatly benefited. Controlling for such effects would increase the effectiveness of this argument.

12A. Assortativity would not only be defined by geographic propinquity. There is well established research on the effect of distance on the establishment and maintenance of ties being U shaped. Longer distances stop having a negative effect to maintaining a tie. In the context of collaborations it stands to reason that academics at UCLA would not only look at Stanford, but also MIT and Oxford for the right collaborator. In other words, as expertise required becomes more specialised (and one assumes the quality of knowledge production increases) the location of experts becomes less relevant.

12B. Similarly, personal homophily in building, maintaining and utilising collaborative ties more likely to be related to a shared code of conduct than location.

12C. Institutional homophily is not as convincing an argument to this reviewer. At the same time there is an argument to be made about institutional isomorphism that would apply to the context of multi-University federations or MUS.

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Reviewer #1: No

Reviewer #2: Yes: Andrew C. Herman

Reviewer #3: No

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Research university assortativity conditions the integration of regional innovation systems

PCSY-D-25-00056R1

Dear Dr. Petersen,

We're pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you'll receive an e-mail detailing the required amendments. When these have been addressed, you'll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Gaoxi Xiao, PhD

Academic Editor

PLOS Complex Systems

Additional Editor Comments (optional):

Two Reviewers have finish reviewing the paper. Both of them are happy with the revised version. I would hence glad to recommend the acceptance of the paper. According to journal's policy, making minor revision as suggested by one of the Reviewers is optional. However, kindly note that no further major revision should be made at this stage. Thanks for the good job in preparing the manuscript.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

Reviewer #4: All comments have been addressed

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2. Does this manuscript meet PLOS Complex Systems's publication criteria? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.

Reviewer #2: Yes

Reviewer #4: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

Reviewer #4: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

Reviewer #4: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?<br/><br/>PLOS Complex Systems does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

Reviewer #4: Yes

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6. Review Comments to the Author<br/><br/>Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: Thanks again for the chance to review this paper.

The authors’ responses and revisions have largely addressed my comments from the first round of review. I am more comfortable now about the potential database confounds and the conceptual linkages in the writing between MUS and RIS.

My only remaining concern is that the lack of context in the case selection has the potential to mislead readers about the results. The authors clearly believe that the results are generalizable in some sense, as the conclusion section speaks broadly about the potential implications to MUS design writ-large. These assumptions should be made explicit. Which findings are the most likely to generalize and why? Which findings are the least likely to generalize and why?

Otherwise it is a strong paper that deserves to be published.

Reviewer #4: (No Response)

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

Do you want your identity to be public for this peer review? If you choose “no”, your identity will remain anonymous but your review may still be made public.

For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

Reviewer #4: No

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