OCLC Research is studying utilization rates of MARC tags and subfields in WorldCat and producing tools and reports to ultimately inform decisions about where we go from here with the data that has been encoded using the MARC standard. The MARC Usage in WorldCat website has been updated with October 2013 reports and with two new data visualizations. One visualization depicts every field by format and then by tag in a zoomable starburst diagram, and the other depicts every field first by tag and then by format in a zoomable starburst. Actual numbers can be seen while hovering over the tag.
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