The Premier Healthcare Database is a privately owned database that represents approximately 1/5th of all United States hospitalizations annually. It includes all International Classification of Diseases-9th Revision (ICD-9) and International Classification of Diseases-Clinical Modification (ICD-9-CM) diagnosis and procedure codes recorded by the hospital, as well as a limited set of Current Procedural Terminology (CPT)-4 codes. Within the database, discharge-level data include information on patient and provider characteristics, diagnoses and procedures, hospital resource utilization, and charges/cost data for all entries, including pharmacy charges.