How do firm boundaries influence employees' acquisition of information? Using detailed project-level data and qualitative evidence, I document that pharmaceutical firms are more likely to outsource the coordination of data-intensive clinical trials, while they are more likely to assign knowledge-intensive trials to internal teams. Managers do not choose between market and hierarchy, but between the hierarchy of the firm—in which subjective performance evaluations are combined with flat explicit incentives—and the hierarchy of its subcontractor—whose virtue stems precisely from the ability to provide high-powered incentives on a narrow set of monitorable tasks.

We estimate the magnitude of spillovers generated by 112 academic "superstars" who died prematurely and unexpectedly, thus providing an exogenous source of variation in the structure of their collaborators' coauthorship networks. Following the death of a superstar, we find that collaborators experience, on average, a lasting 5% to 8% decline in their quality-adjusted publication rates. By exploring interactions of the treatment effect with a variety of star, coauthor, and star/coauthor dyad characteristics, we seek to adjudicate between plausible mechanisms that might explain this finding. Taken together, our results suggest that spillovers are circumscribed in idea space, but less so in physical or social space. In particular, superstar extinction reveals the boundaries of the scientific field to which the star contributes-the "invisible college." (c) 2010 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology..