Upcoding: Evidence from Medicare on Squishy Risk Adjustment


Michael Geruso and Timothy J. Layton. 3/2020. “Upcoding: Evidence from Medicare on Squishy Risk Adjustment.” Journal of Political Economy, 128, 3, Pp. 984-1026. NBER Working Paper


Upcoding—manipulation of patient diagnoses in order to game payment systems—has gained significant attention following the introduction of risk adjustment into US insurance markets. We provide new evidence that enrollees in private Medicare plans generate 6% to 16% higher diagnosis-based risk scores than they would generate under fee-for-service Medicare, where diagnoses do not affect payments. Our estimates imply upcoding generates billions of dollars in excess public spending annually and significant consumer choice distortions. We show that coding intensity increases with vertical integration, reflecting a principal-agent problem faced by insurers, who desire more intense coding from the physicians with whom they contract.

Last updated on 02/22/2021