The sum appropriated pursuant to section 620 of this title for each fiscal year shall be allotted by the Secretary for use by cooperating State public welfare agencies which have plans developed jointly by the State agency and the Secretary as follows: He shall first allot $70,000 to each State, and shall then allot to each State an amount which bears the same ratio to the remainder of such sum as the product of

The “allotment percentage” for any State shall be 100 per centum less the State percentage; and the State percentage shall be the percentage which bears the same ratio to 50 per centum as the per capita income of such State bears to the per capita income of the United States; except that

The allotment percentage for each State shall be promulgated by the Secretary between October 1 and November 30 of each even-numbered year, on the basis of the average per capita income of each State and of the United States for the three most recent calendar years for which satisfactory data are available from the Department of Commerce. Such promulgation shall be conclusive for each of the two fiscal years in the period beginning October 1 next succeeding such promulgation.

For purposes of this section, the term “United States” means the fifty States and the District of Columbia.