34 C.F.R. § 300.808
If the amount available for allocation to States under § 300.807 for a fiscal year is equal to or greater than the amount allocated to the States under section 619 of the Act for the preceding fiscal year, those allocations are calculated as follows:
(a) Except as provided in § 300.809, the Secretary—
(b) For the purpose of making grants under this section, the Secretary uses the most recent population data, including data on children living in poverty, that are available and satisfactory to the Secretary.
(Authority: 20 U.S.C. 1419(c)(2)(A))