¹[116J. Indexation of unit area value.—If, for any reason, the base unit area value of any vacant land, or the base unit area value of any covered space of building, in any group in any ward has not been revised on the completion of a period of three years from the date on which such base unit area values were last determined, it shall be lawful to increase or decrease the base unit area values according to the changes in the consumer price index of urban non-manual workers or such other suitable index as the Government may determine till such revision is made by the Municipal Valuation Committee, and to realize the amount of property tax for such covered space of building or vacant land on the basis of the revised base unit area values.