In April and November of each year, the director of planning shall determine the vacancy rate and the vacancy surplus; if any. New market priced rental units available to the general public; for which a certificate of use and occupancy has been issued since the last vacancy survey, shall be added on a unit-for-unit basis to either reduce the "vacancy deficiency" or increase the "vacancy surplus." (Ord. 1341 NCS §1 (part), 1978.)