<p>Research co-production model – full set of parameter estimates.</p>

We implemented the estimation using STATA 13 including year fixed-effects and robust standard errors; see Eq (3) for the model specification. The dependent variable in each model is the research co-production Jij,t between institutions i and j in year t calculated for publications in the 21-year period 2000-2020. We incorporate the alignment with a 1-year lag, ⋅ , to account for inter-annual variation in research area profiles ; note that research area profiles are calculated using mono-university (denoted by M) publications of institution i, whereas Jij,t are calculated for co-produced publications. Below each point estimate is the associated p-value. See S3 Fig. for the corresponding descriptive statistics and covariance matrix. See Fig 5C for a plot of the interaction coefficients included in model (8) to identify the temporal trend associated with institutional homophily. See Fig 5D for a plot of the interaction coefficients generated by model (8) to identify the temporal trend associated with institutional prestige involving two premier universities (Premij = 2).