Abstract: A computer-implemented method is described for identifying products purchased by individual customers at different merchants. The method comprises: receiving product purchase information from two or more merchants in a pre-defined merchant group; receiving transaction data for a plurality of customers in a pre-defined customer group; comparing details of the product purchase information with details of the transaction data to identify the product purchases associated with individual transactions and storing the association in a database; and extracting information from the database for an individual customer or for each customer in the pre-defined customer group to determine the products the customer(s) purchased from each merchant.