(1) For the purpose of determining any authority's fiscal year spending limit under section 20 (7)(b) of article X of the state constitution, the initial spending base of the authority shall be the amount of revenues collected by the authority from sources not excluded from fiscal year spending pursuant to section 20 (2)(e) of article X of the state constitution during the first full fiscal year for which the authority collected revenues.
(2) For purposes of this section, "fiscal year" means any year-long period used by an authority for fiscal accounting purposes.