4. The community shall provide that the growth in the tax base corresponds to
(1) the positive difference obtained by subtracting the standardized property value established for the reference fiscal year determined under the second paragraph from the standardized property value established in accordance with Division I of Chapter XVIII.1 of the Act respecting municipal taxation (chapter F-2.1) for the current fiscal year; or
(2) the positive sum resulting from the algebraic addition of the positive or negative differences obtained by performing separately, for each fiscal year referred to in section 5, the subtraction as provided in that section as regards the values added to or withdrawn from the property assessment roll.
The community shall determine the reference fiscal year by providing that it is either the third fiscal year preceding the current fiscal year or a fiscal year it fixes. In the latter case, the community may not fix more than one reference fiscal year for the current fiscal years during which the same property assessment roll of Ville de Montréal or Ville de Québec, as the case may be, applies.