1. A system to optimize exchange of data used for third-party content selection, comprising: a data processing system having a keyword selection component, a keyword performance component, and a historic online activity database: the keyword selection component identifies, based on data stored in the historic online activity database, a cluster of client devices that previously performed a plurality of online activities of an online activity type in relation to a product or service context; the keyword selection component determines, based on the data stored in the historic online activity database, from a plurality of keywords, a subset of keywords associated with the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; the keyword performance component determines a performance metric of the subset of keywords based on the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; and the keyword selection component transmits, to a computing device of a third-party content provider, the subset of keywords and the performance metric; wherein a parameter value determined for a first keyword of the subset of keywords based on the performance metric is used to select a content item of the third-party content provider associated with the product or service context responsive to a request for third-party content, the request for third-party content indicative of the first keyword, the selected content item configured for display on a client device.
1. A system to optimize exchange of data used for third-party content selection, comprising: a data processing system having a keyword selection component, a keyword performance component, and a historic online activity database: the keyword selection component identifies, based on data stored in the historic online activity database, a cluster of client devices that previously performed a plurality of online activities of an online activity type in relation to a product or service context; the keyword selection component determines, based on the data stored in the historic online activity database, from a plurality of keywords, a subset of keywords associated with the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; the keyword performance component determines a performance metric of the subset of keywords based on the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; and the keyword selection component transmits, to a computing device of a third-party content provider, the subset of keywords and the performance metric; wherein a parameter value determined for a first keyword of the subset of keywords based on the performance metric is used to select a content item of the third-party content provider associated with the product or service context responsive to a request for third-party content, the request for third-party content indicative of the first keyword, the selected content item configured for display on a client device. 2. The system of claim 1 , comprising a content item selection component configured to: receive, from the computing device of the third-party content provider, the parameter value for the first keyword of the subset of keywords; receive the request for third-party content for display on the client device, the request indicative of the first keyword; select, based on the parameter value, a content item of the third-party content provider associated with the product or service context; and provide the selected content item for display on the client device.