1. A method to adjust demographic data, comprising: generating a first model based on reference demographic data corresponding to panelists and based on second demographic data and behavioral data from a database proprietor, the second demographic data and the behavioral data corresponding to ones of the panelists having user accounts with the database proprietor; using the first model to partition the second demographic data into a plurality of nodes, each node representing a respective subset of the second demographic data; and redistributing at least some of the second demographic data between at least some of the nodes to generate a second model.