(a) compute the ratio of assessed valuation to the full valuation of
taxable real estate on the basis of market value surveys completed
pursuant to article twelve of this chapter;
(b) on the basis of the ratios computed pursuant to subdivision (a),
project increases or decreases in the ratios for years for which the
information has not been developed pursuant to article twelve of this
chapter;
(c) avail itself of appropriate market value information appearing in
its office or acquired in the discharge of its duties pursuant to this
chapter.