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 a demand model for each product at each store in the database, the demand models including model parameters; aggregating 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 the first and second sets of model parameters; 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.