Henceforth, further residential development shall be limited to four hundred (400) dwelling units per calendar year. In any given year, if less than four hundred (400) units are approved or constructed, the unused number may not be carried forward to any future year. (§ 4 of measure N, passed by voters 11-3-1987: Ord. 1911, 1986: § 3 of proposition R, passed by voters 11-7-1978)