22. In any case other than the case contemplated in section 21, the median proportion shall be determined by consecutively performing the operations prescribed in subparagraph 1 to 4 of the first paragraph of that section and the following operations:(1) for each comparable roll, its median proportion determined for the fiscal period in question is subtracted from its median proportion determined for the preceding fiscal period;
(2) for each comparable roll, the difference resulting from the subtraction prescribed in subparagraph 1 is divided by the median proportion of that roll determined for the fiscal period preceding the fiscal period in question, and the quotient thereby obtained must comprise 3 decimals and be transformed into a percentage to constitute a variation;
(3) the average variation is determined among the variations determined under subparagraph 2, and the percentage representing that average variation must comprise one decimal;
(4) the average variation determined under subparagraph 3 is multiplied by the median proportion of the roll of the municipality determined for the fiscal period preceding the fiscal period in question;
(5) if the average variation determined under subparagraph 3 is a negative percentage, the product resulting from the multiplication prescribed in subparagraph 4 is transformed into a positive number and is subtracted from the median proportion of the roll of the municipality determined for the fiscal period preceding the fiscal period in question or, if the variation is a positive percentage, the product is added to that proportion;
(6) the difference resulting from the subtraction or the sum resulting from the addition prescribed in subparagraph 5, as the case may be, is multiplied by the quotient resulting from the division prescribed in subparagraph 4 of the first paragraph of section 21;
(7) the products resulting from the multiplications prescribed in subparagraph 6 of this paragraph and in subparagraph 2 of the first paragraph of section 21 are added together.