; provided that, in the absence of complete actual cost data representing the provision of the full covered benefit during the relevant fiscal years, certified community behavioral health clinics may, at the Secretary’s discretion, use estimated or projected data relating to specific services. Initial payments shall be established without the application of a per visit limit or productivity screen and shall be based on national average costs per unit of service, updated as appropriate by the inflationary adjustment described in subparagraph (C). (C) Payments in subsequent years Payment rates in years after the year of implementation of such system shall be the payment rates in the previous year increased— (i) in the first year after implementation of such system, by the percentage increase in the MEI (as defined in section 1842(i)(3)) for the year involved