Medpar gives the billing information for Medicare. It is publicly available, although there can be a small cost affiliated with data acquisition. In fact, many of the public companies that define patient severity indices rely upon Medpar because it is so readily available. In addition, The Centers for Medicare and Medicaid maintain a data warehouse consisting of patients with a defined chronic disease, and this information, too, is available for a fee. There are multiple forms in Medicare data and we provide the SAS code on how to “unpack” the different forms for use in analysis. We are using the 2005 version of the data. The preprocessing to combine the data was given in Chapter 3. We need to unpack the different sheets of the Medpar data in order to use the information. Once that is done, we can first focus on the inpatient datasets.