(b) In the case of special assessing units as defined in section eighteen hundred one of this chapter, the commissioner shall also ascertain for the purposes of article seven of this chapter the ratio of the assessed valuation to the full valuation of taxable real property for each class of property established under article eighteen of this chapter, which percentages as finally determined as provided in this article shall be the class ratios for each such class.

(c) In the case of special assessing units as defined in section eighteen hundred one of this chapter and approved assessing units and eligible non-assessing unit villages which have adopted the provisions of section nineteen hundred three of this chapter as defined in section nineteen hundred one of this chapter, the commissioner shall further ascertain, for the purposes of section eighteen hundred three-a and subdivision three of section nineteen hundred three of this chapter, the percentage of full value at which taxable real property in each class and each class in each portion has been assessed, which percentage as finally determined as provided in this article shall be the class equalization rate for such class or such class in such portion. 2. In establishing state equalization rates, class ratios and class equalization rates the commissioner may, in its discretion, take testimony and hear proof under oath or otherwise, and may avail itself of all information appearing in its office or acquired in the discharge of its duties and may employ experts or other persons to procure any information required for such purpose. 3. All state equalization rates, special equalization rates, class ratios and class equalization rates established by the commissioner pursuant to law may be expressed to such number of decimal places as the commissioner may determine, provided that the number of decimal places shall be uniform for all state equalization rates, special equalization rates, class ratios and class equalization rates established for assessment rolls completed in the same calendar year. 4. For purposes of this article, the assessment roll of a village that has enacted a local law pursuant to the provisions of subdivision three of section fourteen hundred two of this chapter shall be the copy of the part of the town or county assessment roll used for village tax purposes subsequent to the enactment of such local law and the state equalization rate established by the commissioner for the town or county assessment roll shall be deemed to be the state equalization rate established for the village. 5. State equalization rates established by the commissioner may be based upon such market value survey or surveys as the commissioner may designate for that purpose, subject to the following:

(a) the market value survey or surveys so designated shall be uniform for state equalization rates established for all city and town assessment rolls completed in the same calendar year;

(b) for special assessing units and approved assessing units and eligible non-assessing unit villages which have adopted the provisions of section nineteen hundred three of this chapter, the market value survey or surveys so designated for class equalization rates for any assessment roll shall be the same as those designated for state equalization rates for that assessment roll;

(c) the state equalization rate for the assessment roll of a village whose boundaries are coterminous with the boundaries of a union free school district shall be based upon the same market value survey or surveys as the survey or surveys used for state equalization rates for city and town assessment rolls finally completed and filed in the same calendar year as the assessment roll of such village;

(d) the state equalization rate for a village other than those villages described in subdivision four of this section and paragraph (b) of this subdivision shall be based upon the same market value survey or surveys used for the establishment of the state equalization rate of the appropriate town or county assessment roll.