For the purpose of the provisions of Sections 15102 and 15106 which require that the valuation as shown on the last equalized assessment roll be modified pursuant to Section 41201 or 84201, the “current year” as used in Section 41201 or 84201 shall be deemed to be the latest fiscal year for which there exists a last equalized county assessment roll as ascertained in accordance with Chapter 3 (commencing with Section 2050) of Part 3 of Division 1 of the Revenue and Taxation Code, and the term “two immediately preceding years” shall be deemed to be the two fiscal years immediately preceding the fiscal year for which the last equalized county assessment roll exists. Whenever in any year it becomes necessary to determine the modification under Sections 15102 and 15106, at a time between the date when the assessment roll for that year becomes the last equalized county assessment roll ascertained under Chapter 3 and the date when the factor for the current year is certified and becomes available, the factor for the current year shall be deemed to be 1.00.