Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Given the steady increase in co-authored papers in economics journals, this paper reports a study of the patterns of co-authorship between US universities and colleges. A majority of institutions produce more co-authored than single-authored papers. Contacts with researchers from the same institution are still an important source of co-authored papers, even though slightly decreasing in frequency. The determinants of co-authorship outside the own institution are tested in a gravity model and it is found that distance and other geographical variables do not matter. However, the quality of co-authors' institutions, measured by rankings of institutions, has a significant impact on the number of co-authored papers in top economics journals.