1. A computer-implemented method of estimating demand model parameters, comprising: storing transaction data from customer sales in a database, the transaction data including a product and a store, the database including a hierarchical categorization of the products and the stores; generating, by the computer, a demand model for each product at each store in the database, the demand models including model parameters; aggregating, by the computer, first and second sets of model parameters from a first set of products occupying a first node of the hierarchical categorization and a second set of products occupying a second node of the hierarchical categorization; weighting, by the computer, the first and second sets of model parameters, the weighting of the first and second sets of model parameters includes applying a relative factor based on a first level of the first set of products within the hierarchical categorization and a second level of the second set of products within the hierarchical categorization; and storing the average of the weighted first and second sets of model parameters in the database as the model parameters for a demand model of a new product.