CMS produces the PPS impact files each year as part of the annual update in the hospital prospective payment system. The files contain information that can be used to estimate each hospital's payments for the upcoming federal fiscal year. The variables include current payment parameters (e.g. the applicable wage index for the upcoming fiscal year), hospital characteristics from the most recently filed cost report, and patient characteristics from Medicare claims data from two years prior (e.g. the FY2001 impact file is based on MEDPAR data for FY 1999). Relative to the cost report data, the information is timelier and allows a direct estimation of prospective payments (including DSH) by federal fiscal year.