This dissertation studies the U.S. healthcare market, with a focus on provider behaviors and their implications for market efficiency. ^ The first chapter examines physician learning and treatment choices. Physicians often choose among alternative treatment options based on their beliefs over the treatment effectiveness and their skills in delivering the treatment. I examine how two kinds of physician learning jointly shape their treatment choices: Bayesian learning that updates beliefs about treatment-patient match values and learning by doing that improves surgical skills. Using case-level data on the history of brain aneurysm treatments by over 200 physicians, I find that both kinds of learning are present and that physicians are forw...