Abstract: A method and system for allocating inventory in an Internet environment is provided. A method employed by the system may include generating several inventory pools, where each inventory pool represents a number of impressions deliverable to different groups of users characterized by attributes. Impressions deliverable to users represented by each inventory pool may be allocated to each inventory pool. Impressions that correspond to multiple pools may be distributed between the multiple pools. The inventory pools may be stored to a database. Afterwards, and order may be received. The order may include parameters that define an audience and a number of impressions. The number of impressions in the order may be allocated from pools in the database.