1. A method, comprising: obtaining, by a processor, an input data set reflecting online actions of a plurality of online users, wherein the plurality of online users are selected according to a panel selection process based on a statistical process of analyzing demographic characteristics of the online users, wherein the input data set includes a plurality of timestamps associated with the clickstream activity; analyzing, by the processor, the data set to identify characteristics of cross-shopping behavior of the users between different brands of products; and modifying an off-line marketing promotion that includes an offline incentive for buying a particular brand of product based on the identified characteristics, wherein the offline promotion include a process for offline presentation of a media item, and wherein the statistical process comprises: conducting a survey of user demographics in an initial panel of users, determining a current statistic related to the user demographics in the initial panel of users, comparing the current statistic to a statistic corresponding to a historical panel of users for updating the current statistic, and selecting the plurality of online users in the current panel of users from the initial panel of users based on the updated current statistic and the user demographics.