1. A system comprising: one or more processing devices; one or more storage devices storing instructions that, when executed by the one or more processing devices, cause the one or more processing devices to perform the following operations: access a first set of usage data for a first set of resources on a network, the first set of resources having been accessed by a first group of client systems and the first set of usage data being determined based on information received from the first group of client systems sent as a result of beacon instructions included with the first set of resources; access a second set of usage data for a second set of resources on a network, the second set of usage data being determined based on information received from monitoring applications installed on a second group of client systems that accessed the second set of resources, wherein users of the second group of client systems are a sample of a larger group of users that use resources on the network; determine initial usage measurement data for a third set of resources on the network based on the first set of usage data, wherein the third set includes one or more common resources that are included in the first set of resources and the second set of resources; determine, based on the second set of usage data, one or more adjustment factors configured to correct inaccuracies in the determined initial usage measurement data; apply the one or more adjustments factors to the initial usage measurement data to generate adjusted usage measurement data; generate one or more reports based on the adjusted usage measurement data.