1. A system comprising: one or more computers being operable to store: retail data associated with a first entity, the retail data including data from a first data source and a second data source, the retail data further including product identifiers; retail data associated with a second entity, the retail data including product identifiers, the retail data including data from a third data source; and a plurality of factor calculations; wherein one or more of said computers contains business logic that is operable to: identify and retrieve, based on the product identifiers, a plurality of overlapping attribute segments to use for comparing the data from the first and second data sources, compare the plurality of the overlapping attribute segments, calculate a plurality of factors for each of the overlapping attribute segments, each factor representing a bias present in the second data source, and use the factors to adjust the values in the retail data from the third data source, thereby reduce bias present in the third source.