making such a determination, and the geographic regions applied for purposes of this subparagraph (E) of section 2719A(b)(3), as amended by subsection (a) of this section. (f) Effective date The amendments made by subsections (a) and (b) shall apply with respect to plan years beginning on or after January 1, 2021. 3. Government Accountability Office study on profit- and revenue-sharing in health care (a) Study Not later than 1 year after the date of enactment of this Act, the Comptroller General of the United States shall conduct a study to— (1) describe what is known about profit- and revenue-sharing relationships in the commercial health care markets, including those relationships that— (A) involve one or more— (i) physician groups that practice within a hospital included in the profit- or revenue-sharing relationship, or refer patients to such hospital