If your account subscribes to Essentials Collections or has purchased Add-on Content (see more info here), you may wish to determine how much this content is being used. Although there is no single report that shows usage by collection, you can compare the COUNTER TR report with an export of your Admin title list, which does show the collection name for each title, to get a sense of which collections' titles are being used. Credo support will prepare a formal report using this data on request to support@credoreference.com, just let us know what reporting time period you're interested in.
See more about running usage reports here.