Administrative Data Systems
One of the earliest systems available was the National Hospital Discharge Survey, created and maintained by the National Center for Health Statistics (NCHS).
Begun in 1965, it relied largely on medical record abstracting of discharges in sampled hospitals. By 1985 it was contributed to by most hospitals and states, who volunteered electronic data that was routinely generated by hospitals in a standardized format. The NCHS undertook other standing surveys of medical care utilization, such as the national ambulatory medical care survey (NAMCS) and the National Hospital Ambulatory Medical Care Survey (NHAMCS), early versions of which are all housed at the Inter-University Consortium for Political and Social Research (ICPSR). The annual summaries are accessible for research uses directly from the internet at the National Center for Health Statistics.
Figure 1 illustrates the kind of long-term data that can be derived from the National Hospital Discharge Survey. This figure shows how NHDS provides information on the changes in length of stay over a long period of time.