7 C.F.R. § 1940.565
(b) Basic formula criteria, data source and weight. See § 1940.552(b) of this subpart. The criteria used in the basic formula are:
(5) State's percentage of the National number of rural households below 50 percent of the area median income.
Data source for each of these criteria is based on the latest census data available. Each criterion is assigned a specific weight according to its relevance in determining need. The percentage representing each criterion is multiplied by the weight factor and summed to arrive at a basic State factor (SF)
SF = (criterion 1 × weight of 25%) + (criterion 2 × weight of 10%) + (criterion 3 × weight of 15%) + (criterion 4 × weight of 30%) + (criterion 5 × weight of 20%)
(h) Pooling of funds. See § 1940.552(h) of this subpart.