A current behavioral targeting system is first tested using a suite of test data. The output of the test is one or more performance metrics. Next, newly proposed behavioral targeting system created. The newly proposed behavioral targeting system is then evaluated using both the existing source data and a new source data. The evaluation of the newly proposed behavioral targeting system produces one or more performance metrics of the same type earlier calculated. Finally, the two sets of performance metrics are compared. The performance metric difference represents the impact of the new source data.