rolling average

… so that a 36-month rolling average utility consumption per unit per month under paragraph (c)(1) of this section can be determined.

(f) You must demonstrate continuous compliance on a 12-month rolling average basis determined at the end of every month (12 times per year) according to paragraphs (f)(l) and (2).

The simplest spending formula applies a constant spending rate to a moving (or rolling) average of the market value of the endowment over several prior years.

10-year rolling average