Finally, observe that the homophily in general grows when the granularity of the node class moves from "university" to "region", indicating that the geographic aspect plays an important role in the formation of collaborations.
Comparing the two types of factors, we find that network-endogenous factors are predominant in the formation of new collaborations in each of the collaboration networks analyzed in this study.
These are known to have a positive impact on productivity [32] and to be a driving force in the formation of new collaborations [7].
The results presented here have important implications for the formation of distributed collaborations and, in particular, to educational institutions offering distance-learning programs that require team projects.
Also troubling is the potential for the visa system as it currently operates to harm the research enterprise in the United States by stymieing the flow of scientific information and the formation of international collaborations.
It is certainly the case that funding dedicated to supporting such research endeavors is a strong catalyst to the formation of these collaborations.
That is, the initial efforts in forming collaborations across a variety of disciplines are crucial so much so that in-person meetings are more than justified and as importantly, the initial formation of such collaborations should be focused on facilitating approaches and channels of communication that can be used to address a mutual problem (Karsai and Knisley, 2010).
For example, Brueton et al examined other ways of assessing the value of methodological research, such as the applications of a piece of work, further developments of the research, release of software and provision of guidance materials to facilitate uptake, formation of new collaborations, and broad dissemination.
Given the value of systematic reviews for clinicians and health policymakers, we suggest the formation of a Cochrane Collaboration review group focused on orphan drugs as one way of reducing these gaps in knowledge.
We use research administration data on human subject protection, animal use management, and grant funding applications to construct new measures of collaboration formation and success.
We hope this model of collaboration formation can be used to guide similarly minded endeavors in other countries.
