Abstract: At least one aspect is directed to identifying in-market activity for content placement as part of an online content item placement campaign. A data processing system can determine renderings of online documents by an end user computing device within a time period, and can classify the online documents into a top level subject matter category. At least one of a plurality of sub-categories of the top level subject matter category can be identified as an in-market category that includes some of the online documents. A number of renderings of the plurality of online documents during the time period, and a number of conversions associated with the renderings can be determined A score can be assigned to the end user computing device based on the number of renderings and the number of conversions. Based on the score, the end user computing device can be classified as in-market or out of market.