3010.21—Calculation of annual limitation.
(a)
The calculation of an annual limitation involves three steps. First, a simple average CPI-U index is calculated by summing the most recently available 12 monthly CPI-U values from the date the Postal Service files its notice of rate adjustment and dividing the sum by 12 (Recent Average). Then, a second simple average CPI-U index is similarly calculated by summing the 12 monthly CPI-U values immediately preceding the Recent Average and dividing the sum by 12 (Base Average). Finally, the annual limitation is calculated by dividing the Recent Average by the Base Average and subtracting 1 from the quotient. The result is expressed as a percentage, rounded to three decimal places.
(b)
The formula for calculating an annual limitation is as follows: Annual Limitation = (Recent Average/Base Average)−1.