Does Co-authorship Lead to Higher Academic Productivity?

In recent decades, co-authorship and policies aimed at inducing academic collaboration have increased simultaneously. Assuming that intellectual collaboration is exogenously determined, prior studies found a negative relationship between co-authorship and productivity. I examine a panel data on economists publishing from 1970 to 2011 to test the causal effect of intellectual collaboration on intellectual output. As characteristics of the individual and her opportunity set are endogenously related to both collaboration and productivity, I instrument the amount of co-authorship by the common research interest between an author and her potential co-authors. After controlling for endogenous co-authorship formation, unobservable heterogeneity and time varying factors, the effect of intellectual collaboration on individual performance becomes positive.