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 that is separate from a first entity, the reference demographic data collected from the panelists by the first entity and stored by the first entity, and 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; redistributing at least some of the second demographic data between at least some of the nodes to generate a second model; applying the second model to third demographic data of the database proprietor; and based on an output of the second model, determining whether to adjust at least some of the third demographic data.