“The goal of this new MARC Usage in WorldCat activity is to provide an evidence base for testing assertions about the value of capturing various attributes by demonstrating whether the cataloging community has made the effort to populate specific tags, not just to define them in anticipation of use. OCLC Research seeks to use evidence of usage, as depicted in WorldCat, the largest aggregation of library data in the world, to inform decisions about where we go from here with the data that has been encoded using the MARC standard. Senior Program Officer Roy Tennant is leading this work by utilizing a process similar to “ground truthing” whereby geographic remote sensing data is checked or enhanced by on-the-ground observation and measurement. He and his team are attempting to perform a similar function for library cataloging. The MARC standard has been used for many decades, but how, exactly? Which elements and subfields have actually been utilized, and more importantly, how? Outputs of these efforts will include quarterly web reports on the usage of MARC within WorldCat throughout 2013, reports as requested for WorldCat Quality Control and/or the Library of Congress Bibliographic Framework Transition Initiative.”