; provider network (A) Subsequent periods Beginning with 2021 and for subsequent years, the Secretary shall continue to use an administrative process to set such rates in order to promote payment accuracy, to ensure adequate beneficiary access to providers, and to promote affordability and the efficient delivery of medical care consistent with subsection (a)(1). Such rates shall not be set at levels expected to increase average medical costs per enrollee covered under the public health insurance option beyond what would be expected if the process under paragraph (1)(B) were continued, as certified by the Office of the Actuary of the Centers for Medicare & Medicaid Services. (B) Establishment of a provider network Health care providers participating under Medicare are participating providers in the public health insurance option unless they opt out in a process established by the Secretary. (3) Administrative process for setting rates Chapter 5 of title 5, United States Code, shall apply to the process for the initial establishment of payment rates under this subsection but not to the specific methodology for establishing such rates or the calculation of such rates. (4) Construction Nothing in this section shall be construed as limiting the Secretary’s authority to correct for payments that are excessive or deficient, taking into account the provisions of subsection (a)(1) and any appropriate adjustments based on the demographic characteristics of enrollees covered under the public health insurance option, but in no case shall the correction of payments under this paragraph result in a level of expenditures per enrollee that exceeds the level of expenditures that would have occurred under paragraph (1)(B), as certified by the Office of the Actuary of the Centers for Medicare & Medicaid Services. (5) Construction Nothing in this section shall be construed as affecting the authority of the Secretary to establish payment rates, including payments to provide for the more efficient delivery of services, such as the