Under Medicare Part A, payment for acute care hospital inpatient stays is based on set rates. This system for payment– the inpatient prospective payment system (IPPS)–categorizes cases into diagnosis-related groups (DRGs) which are then weighted based on resources used to treat Medicare beneficiaries in those groups. Important for safety net providers, hospitals that treat a large share of low-income patients receive additional add-on payment in the form of a disproportionate share hospital (DSH) adjustment. Teaching hospitals also receive additional add-on payments, which are based on resident to average daily census ratios. The IPPS rule is updated annually, with comment periods open prior to implementation of the final rule.