We have been tracking the use of the MARC standard, as evidenced in WorldCat records (now well over 400 million!) for six years. Not only have we reported on how often a tag and its constituent subfields have been used (even ones that shouldn’t exist), but for selected subfields we have also reported on its contents.
If errors are detected, such as subfields being used that are not defined in the MARC standard, I will sometimes run a report so that our WorldCat Quality Control staff can make the needed corrections. Something similar happened recently, when I discovered that a field that had been deprecated and had been slowly going away had achieved new life and was coming back. It turned out that one institution hadn’t received the memo, so we cleaned up the mess and asked them to desist.
But error detection isn’t the only reason to do this work. If we are to make a smooth transition to a world of linked data, we need to know what we have to work with. These reports are meant to expose exactly what we have to work with, in the aggregate, so we can make informed decisions.
It’s also possible to track the growth in the use of the newly-defined RDA fields using these reports, such as the 33Xs. For example, there were less than 200,000 records that had a 336 in 2013, but by five years later there were over 266 million. In contrast, use of the 258 Philatelic Issue Data field went from 8 appearances in 2013 to 19 in 2018. Not exactly meteoric.
Since it isn’t practical, or meaningful, for us to produce these reports for every subfield, we focus on the ones that seem most useful to report on. But if there is a subfield that you want to know more about, just request it.
Information is power.