State Share = [(State per capita income)2/(National per capita income)2] * 45 percent
Federal share = 100 percent minus the State share (with a minimum of 50 percent and a maximum of 83 percent)
The formula provides for squaring both the State and national average per capita incomes; this procedure magnifies any difference between the State's income and the national average. Consequently, Federal matching to lower income States is increased, and Federal matching to higher income States is decreased, within the statutory 50-83 percent limits. The FMAP for Puerto Rico, the Virgin Islands, Guam, the Northern Mariana Islands, and American Samoa is set by statute at 50 percent and is subject to dollar limitations specified in section 1108 of the Act.
42 C.F.R. §433.10
Sections 1902(a)(10), 1933 of the Social Security Act (42 U.S.C. 1396a ), and Pub. L. 105-33