I'm not certain that I have the logic for this quite right. (Suggestions welcome!)
But with that understanding: I had a program run backwards through the weekly LC names issues, from the present issue (2016.30) back through 2010.1, looking for the most recent appearance of each LCCN. (There's an exception to this "most recent issue" question, as noted below.) That most recent issue of an LCCN had to be an "update". Of such records, the program was only interested in those with 100 fields whose last subfield was $d, and which contained a death date. These records form the pool of candidates. (There were 203,544 such candidates.) The 100 field as found became the "new heading", and the 100 field minus the death date became the "old heading".
If the latest version of the candidate record contains a 4XX for the old heading, the program writes a report to that effect, and it's done with that record.
If the latest version of the candidate record does not contain a 4XX for the old heading, the program makes a note of the LCCN, and both the old and new headings. In its backwards scan of records, the program looks for earlier representations of the record with this LCCN; if it finds such, it tests the 100 field to see if it's the same as the "old heading." (If this happens, that means that the 100 was later changed to add the death date, with no other changes.)
Assuming that I've got the logic right, this scan found 203,544 candidate records. Of these, 2,565 represent changed headings where the only change involved the addition of a death date and a 400 for the former heading is present. (In case anyone is interested: in 37 of these records there was no subfield $w, making the need for the 400 less than obvious.) Another 5,967 represent changed headings where the only change involved the addition of a death date and no 4XX for the former heading is present.
Gary L. Strawn
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authority toolkit documentation: http://bit.ly/1Hl1jST
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When we add a death date to the personal name authority, we don’t add a 4XX for the open date. At least I don’t, and I haven’t seen that being done. So based on that, I wouldn’t add a 4XX with the open date for the name/title variants either.