outside researchers using Medicare Provider Analysis and Review (MEDPAR) data. The DRG system, which was originally intended to facilitate utilization reviews by identifying aberrant cases, or outliers, was first reported 35 years ago6 and first used as a payment mechanism in New Jersey in 1980.

The information available today is much richer than that available when the Dartmouth Atlas first appeared, and research interest continues to grow. The value of CMS data is limited by the fact that they reflect only care delivered to Medicare and to a certain extent Medicaid beneficiaries. The availability of more universal data will serve to enhance greatly the understanding of the functioning of the U.S. health care system.


6 John D. Thompson, Robert B. Fetter, and Charles D. Mross, 1975, “Case Mix and Resource Use,” Inquiry 12(4):300-312.

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