Using Research-Interest Similarity and Departmental Co-membership to Predict Collaborative Ties

I investigate the complimentary roles of similarity on research interests, and of departmental co-membership on promoting new collaborative ties among professors at an elite American research university. Similarity is measured as cosine similarity of tf-idf calculations of their abstracts for published work, and is recalculated for each year in the study period. I find that similarity is a strong predictor of collaboration, but that department comembership is even stronger.