Payment rates in Medicare's Prospective Payment System (PPS) are based on averages of historical hospital costs. Compared to reimbursing each hospital's own costs, pricing at the average of costs implies a massive redistribution of payments among hospitals. Because not all sources of hospital costs are accounted for in the PPS, some of this redistribution is ‘unfair’. Information in hospital-specific costs on unmeasured patient severity and input prices can be exploited to reduce payment inequities. However, fully hospital-specific rates are not optimal because costs also reflect treatment intensity and efficiency differences among hospitals.
