The most recent AHA survey available for our report was for 1999. In completing the survey, hospitals are requested to report data for a full year based on their fiscal year (so that the reporting period should be consistent with Medicare cost report data). Overall, the average response rate is about 82 percent. However, the response rate on many of the financial items relevant for our purposes is about 65 percent and is not necessarily representative of the universe of hospitals (e.g. proprietary hospitals have a lower response rate for financial data). This makes it difficult to analyze data within states or market areas. Estimates are made of data for non-reporting hospitals and for reporting hospitals that submit incomplete AHA Annual Survey questionnaires. Payer mix and revenue information is confidential and is not available on the public use file. On the non-confidential file, inpatient utilization information by payer is available for Medicare and Medicaid patients but not for other payers.