Abstract: This disclosure concerns a hybrid method for estimating Internet traffic including determining a fraction of a target population consisting of users displaying an identified characteristic by analysis of a census-based measurement of internet traffic for at least one website and receiving their clickstream data. The method also includes identifying a fraction of the group of participants that share the one or more characteristics, determining a behavioral composition by scaling the fraction of the group of participants by the fraction of the target population, and producing, at the host processing facility, an estimate of the target population's activity with respect to at least a part of the Internet that includes the at least one website by scaling the clickstream data for the subset of the group of participants by applying a weight based on the behavioral composition and the relative size of the target population.