We investigate the role of physician agency and competition in determining health care supply and patient outcomes. A 2005 change to Medicare fees had a large, negative impact on physician profit margins for providing chemotherapy treatment. In response to these cuts, physicians increased their provision of chemotherapy and changed the mix of chemotherapy drugs they administered. The increase in treatment improved patient survival. These changes were larger in states that experienced larger decreases in physician profit margins. Finally while physician response was larger in more competitive markets, survival improvements were larger in less competitive markets.
Jacobson, Mireille, Tom Y. Chang, Joseph P. Newhouse, and Craig C. Earle. "Physician Agency and Competition: Evidence from a Major Change to Medicare Chemotherapy Reimbursement Policy." NBER Working Paper 19247, July 2013.