42 CFR §413.231

1. (a)CMS adjusts the labor-related portion of the base rate to account for geographic differences in the area wage levels using an appropriate wage index (established by CMS) which reflects the relative level of wages relevant to the furnishing of renal dialysis services in the geographic area in which the ESRD facility is located.
2. (b)The application of the wage index is made on the basis of the location of the ESRD facility in an urban or rural area as defined in this paragraph (b).
   1. (1)Urban area means a Metropolitan Statistical Area or a Metropolitan division (in the case where a Metropolitan Statistical Area is divided into Metropolitan Divisions), as defined by OMB.
   2. (2)Rural area means any area outside an urban area.
3. (c)Beginning January 1, 2023, CMS applies a cap on decreases to the wage index, such that the wage index applied to an ESRD facility is not less than 95 percent of the wage index applied to that ESRD facility in the prior calendar year.
4. (d)Beginning January 1, 2023, CMS applies a floor of 0.6000 to the wage index, such that the wage index applied to an ESRD facility is not less than 0.6000.