1. A computer-implemented method, comprising: accessing, by a reporting server, site-centric usage data representing resource accesses on a network by client devices in a plurality of households, wherein the site-centric usage data results from beacon instructions executed by content-presenting applications on the client devices from which the resource accesses originate, wherein the beacon instructions are configured to cause an executing client device to send a message to a collection server, and wherein the content-presenting applications on the client devices that execute the beacon instructions are otherwise unaffiliated with the collection server; based on the accessed site-centric usage data, determining, by the reporting server, candidate households that the site-centric usage data indicates are associated with resource accesses from one or more persistent IP addresses, wherein an IP address is a persistent IP address when the IP address has been assigned to and associated with resources accesses from only one of the households in the set of households for at least a threshold period of time; based on the accessed site-centric usage data, determining, by the reporting server, a set of the candidate households that the site-centric usage data indicates are at least associated with a first specified number of a first type of client device and a second specified number of a second type of client device; extracting, by the reporting server, a subset of the site-centric usage data, the subset corresponding to resource accesses by client devices associated with the set of candidate households; and based on the extracted subset of the site-centric usage data, determining, by the reporting server, a measure of overlap that estimates an amount of users that have accessed the same resource using a first type of client device and a second type of client device.