; and (ii) the difference between the overall average percentage of the locality-based comparability payments taking effect in fiscal year 2018 under section 5304 of such title (whether by adjustment or otherwise), and the overall average percentage of such payments which was effective in the previous fiscal year under such section. (2) Notwithstanding any other provision of law, no prevailing rate employee described in subparagraph (B) or (C) of section 5342(a)(2) of title 5, United States Code, and no employee covered by section 5348 of such title, may be paid during the periods for which paragraph (1) is in effect at a rate that exceeds the rates that would be payable under paragraph (1) were paragraph (1) applicable to such employee. (3) For the purposes of this subsection, the rates payable to an employee who is covered by this subsection and who is paid from a schedule not in existence on September 30, 2017, shall be determined under regulations prescribed by the Office of Personnel Management. (4) Notwithstanding any other provision of law, rates of premium pay for employees subject to this subsection may not be changed from the rates in effect on September 30, 2017, except to the extent determined by the Office of Personnel Management to be consistent with the purpose of this subsection. (5) This subsection shall apply with respect to pay for service performed after September 30, 2017. (6) For the purpose of administering any provision of law (including any rule or regulation that provides premium pay, retirement, life insurance, or any other employee benefit) that requires any deduction or contribution, or that imposes any requirement or limitation on the basis of a rate of salary or basic pay, the rate of salary or basic pay payable after the application of this subsection shall be treated as the rate of salary or basic pay. (7) Nothing in this subsection shall be considered to permit or require the payment to any employee covered by this subsection at a rate in excess of the rate that would be payable