Where:	AAPCC	=	adjusted average per capita cost
	USPCC	=	U.S. average per capita cost to the Medicare program
	$$\frac{\mathit{\text{APC}}{C}_{Co}}{\mathit{\text{APC}}{C}_{US}}$$	=	ratio of per capita reimbursement in the county to the United States(5-year average)
And:	U	=	a unique underwriting index which represents the ratio of risk for a particular subset of the Medicare population to the national average. Thirty population subsets are defined by the four variables: age (five groups), sex (two groups), and institutional and welfare status (three groups).
	E	=	the number of Medicare beneficiaries in a unique underwriting index cell.