Online advertising is increasingly becoming more performance oriented, where the decision to show an advertisement to a user is made based on the user’s propensity to respond to the ad in a positive manner (e.g., purchasing a product, subscribing to an email list, etc). The user response depends on how well the ad campaign matches the user’s interest, as well as the amount of the user’s past exposure to the campaign – a factor shown to be impactful in controlled experimental studies. Past exposure builds brand-awareness and familiarity with the user, which in turn leads to a higher propensity of the user to buy/convert on the ad impression. In this paper we propose a model of the user response to an ad campaign as a function of both interest match and past exposure, where the interest match is estimated using historical search/browse activities of the user. The goal of this paper is two-fold. First, we demonstrate the role played by the user interest and the past exposure in m...