The per centum of exemption allowed by Real
Property Tax Law § 485-b, Subdivision 2(a)(i), in which
real property constructed, altered, installed or improved subsequent
to July 1, 1976, for the purpose of commercial, business or industrial
activities is granted an exemption from taxation and special ad valorem
levies to the extent of 50% of the increase in assessed value thereof
attributable to such construction, alteration, installation or improvement,
is hereby reduced from 50% to zero.
This article reducing the per centum of exemption
shall not apply to a project in the course of construction or exemptions
existing prior to the adoption of this article.