(1) The department must calculate a county wide wage index each rebase year by utilizing the most recent average wage data available from the federal bureau of labor statistics for registered nurses, licensed practical nurses, and certified nursing assistants.

(2) For each county, the department must calculate an average combined wage for all three disciplines based on the percentage of total wages by discipline from the prior year cost report. Each wage must be multiplied by the relative utilization percentage for that discipline. The total of all three disciplines is the average wage in that county.

(3) The department must calculate the statewide average combined wage for all three disciplines based on the average percentage of total wages by discipline from the prior year cost report.

(4) The county index is determined by dividing the county average wage in a given county by the statewide average wage.