Table 1. Description of data used in analyses.

Data Source	Number of institutions	Date range	Variables collected
Subset of Emergency Departments with ICD-9 Discharge Codes	11	1/1/2000–6/30/2002	Date of visit
			Hospital name
			Age
			Sex
			Chief complaint
			ICD-9 discharge code
All Emergency Departments	50	1/1/2004–12/21/2006	Date of visit
			Hospital name
			Age
			Sex
			Chief complaint
Hospitals	76	1/1/2004–12/21/2006	Date of admission
			Date of discharge
			Type of admission
			Hospital identification
			Age
			Sex
			ICD-9 discharge code