Measuring hospital cost-sharing incentives under refined prospective payment

This paper evaluates the usefulness of a model (McClellan, 1997) that was recently proposed for measuring reimbursement incentives under ongoing refinements to the hospital prospective payment system. The model is applied to a single major disease category HIV infection for which the hospital reimbursement system has undergone dramatic refinements in recent years. The paper highlights a problem in the original specification, namely, the use of endogenous costs as an explanatory variable. The paper illustrates how hospital response to both marginal price incentives (e.g., a change in the supply of payment-related services) and average price incentives (e.g., a change in the supply of non-payment-related services) can cause either over- or underestimation of payer cost sharing. In the present case study, overestimation of the marginal reimbursement incentives was evidenced. Obtaining cost-sharing estimates that can be used to evaluate alternative payment classification systems requires controlling for endogenous changes in hospital behavior.