Pennsylvania hospitals are required by law to submit certain information to the PHC4. The 1998 data compiled for the purpose of this publication is reported as it was submitted to the PHC4 by Pennsylvania hospitals. The data was subject to standard verification processes by the PHC4. In addition, hospitals are required to submit data indicating in simple terms "how sick the patient was," or in technical jargon, a "severity score." The data are then risk-adjusted.