1. A system for determining product availability in an inventory that includes numerous products defined by a set of attributes, comprising: a data structure in memory comprising a plurality of aggregated forecast vectors that for a period of time provide a forecasted number of units of a product in each of a number of inventory regions, wherein each region is defined by a subset of the attributes and wherein an inventory element is determined to have the attributes of one or more of the subsets and is counted in each of the regions with corresponding attributes; and a data processor running an inventory management module in communication with the memory for processing a request from an order management system by determining a unique product identifier from the request and returning one or more of the aggregated forecast vectors associated with the unique product identifier and for providing reports including at least portions of the aggregated forecast vectors to a selection module for use in selecting inventory elements for use by a delivery system.