We measure organizational concentration—the distribution of a patient's healthcare across organizations—to examine how firm boundaries affect healthcare efficiency. First, when patients move to regions where outpatient visits are typically concentrated within a small set of firms, their...

We measure provider coverage networks for plans on the Massachusetts health insurance exchange using a two measures: consumer surplus from a hospital demand system and the fraction of population hospital admissions that would be covered by the network. The two measures are highly correlated, and...

Patients often receive healthcare from providers spread across different firms. Transaction costs, imperfect information, and other frictions can make it difficult to coordinate production across firm boundaries, but we do not know how these challenges affect healthcare. We define and measure...